The influences of fluorine and process variations on polysilicon film stress and MOSFET hot carrier effects

Science.gov (United States)

Lowry, Lynn E.; Macwilliams, Kenneth P.; Isaac, Mary

1991-01-01

The use of fluorinated gate oxides may provide an improvement in nMOSFET reliability by enhancing hot carrier resistance. In order to clarify the mechanisms by which polysilicon processing and fluorination influence the oxide behavior, a matrix of nMOSFET structures was prepared using various processing, doping, and implantation strategies. These structures were evaluated for crystalline morphology and chemical element distribution. Mechanical stress measurements were taken on the polysilicon films from room temperature to cryogenic temperature. These examinations showed that fluorination of a structure with randomly oriented polysilicon can reduce residual mechanical stress and improve hot carrier resistance at room temperature.

Near-infrared free carrier absorption in heavily doped silicon

International Nuclear Information System (INIS)

Baker-Finch, Simeon C.; McIntosh, Keith R.; Yan, Di; Fong, Kean Chern; Kho, Teng C.

2014-01-01

Free carrier absorption in heavily doped silicon can have a significant impact on devices operating in the infrared. In the near infrared, the free carrier absorption process can compete with band to band absorption processes, thereby reducing the number of available photons to optoelectronic devices such as solar cells. In this work, we fabricate 18 heavily doped regions by phosphorus and boron diffusion into planar polished silicon wafers; the simple sample structure facilitates accurate and precise measurement of the free carrier absorptance. We measure and model reflectance and transmittance dispersion to arrive at a parameterisation for the free carrier absorption coefficient that applies in the wavelength range between 1000 and 1500 nm, and the range of dopant densities between ∼10 18 and 3 × 10 20  cm −3 . Our measurements indicate that previously published parameterisations underestimate the free carrier absorptance in phosphorus diffusions. On the other hand, published parameterisations are generally consistent with our measurements and model for boron diffusions. Our new model is the first to be assigned uncertainty and is well-suited to routine device analysis

Mid-infrared plasmonic resonances exploiting heavily-doped Ge on Si

Science.gov (United States)

Biagioni, P.; Sakat, E.; Baldassarre, L.; Calandrini, E.; Samarelli, A.; Gallacher, K.; Frigerio, J.; Isella, G.; Paul, D. J.; Ortolani, M.

2015-03-01

We address the behavior of mid-infrared localized plasmon resonances in elongated germanium antennas integrated on silicon substrates. Calculations based on Mie theory and on the experimentally retrieved dielectric constant allow us to study the tunability and the figures of merit of plasmon resonances in heavily-doped germanium and to preliminarily compare them with those of the most established plasmonic material, gold.

Boron diffusion into nitrogen doped silicon films for P{sup +} polysilicon gate structures

Energy Technology Data Exchange (ETDEWEB)

Mansour, Farida; Mahamdi, Ramdane; Jalabert, Laurent; Temple-Boyer, Pierre

2003-06-23

This paper deals with the study of the boron diffusion in nitrogen doped silicon (NIDOS) deposited from disilane Si{sub 2}H{sub 6} and ammonia NH{sub 3} for the development of P{sup +} polysilicon gate metal oxide semiconductor (MOS) devices. NIDOS films with varied nitrogen content have been boron implanted, then annealed and finally analysed by secondary ion mass spectroscopy (SIMS). In order to simulate the experimental SIMS of boron concentration profiles in the NIDOS films, a model adapted to the particular conditions of the samples elaboration, i.e. the very high boron concentration and the nitrogen content, has been established. The boron diffusion reduction in NIDOS films with increasing nitrogen rates has been evidenced by the profiles as well as by the obtained diffusion coefficients, which shows that the nitrogen incorporation reduces the boron diffusion. This has been confirmed by capacitance-voltage (C-V) measurements performed on MOS capacitors: the higher the nitrogen content, the lower the flat-band voltage. Finally, these results demonstrate that the improvement of the gate oxide quality occurs with the suppression of the boron penetration.

Self-Assembled Formation of Well-Aligned Cu-Te Nano-Rods on Heavily Cu-Doped ZnTe Thin Films

Science.gov (United States)

Liang, Jing; Cheng, Man Kit; Lai, Ying Hoi; Wei, Guanglu; Yang, Sean Derman; Wang, Gan; Ho, Sut Kam; Tam, Kam Weng; Sou, Iam Keong

2016-11-01

Cu doping of ZnTe, which is an important semiconductor for various optoelectronic applications, has been successfully achieved previously by several techniques. However, besides its electrical transport characteristics, other physical and chemical properties of heavily Cu-doped ZnTe have not been reported. We found an interesting self-assembled formation of crystalline well-aligned Cu-Te nano-rods near the surface of heavily Cu-doped ZnTe thin films grown via the molecular beam epitaxy technique. A phenomenological growth model is presented based on the observed crystallographic morphology and measured chemical composition of the nano-rods using various imaging and chemical analysis techniques. When substitutional doping reaches its limit, the extra Cu atoms favor an up-migration toward the surface, leading to a one-dimensional surface modulation and formation of Cu-Te nano-rods, which explain unusual observations on the reflection high energy electron diffraction patterns and apparent resistivity of these thin films. This study provides an insight into some unexpected chemical reactions involved in the heavily Cu-doped ZnTe thin films, which may be applied to other material systems that contain a dopant having strong reactivity with the host matrix.

Very heavily electron-doped CrSi2 as a high-performance high-temperature thermoelectric material

International Nuclear Information System (INIS)

Parker, David; Singh, David J

2012-01-01

We analyze the thermoelectric behavior, using first principles and Boltzmann transport calculations, of very heavily electron-doped CrSi 2 and find that at temperatures of 900-1250 K and electron dopings of 1-4 × 10 21 cm -3 , thermopowers as large in magnitude as 200 μV K -1 may be found. Such high thermopowers at such high carrier concentrations are extremely rare, and suggest that excellent thermoelectric performance may be found in these ranges of temperature and doping. (paper)

Polysilicon tft's fabricated by crystallization of a-si:h enhanced by hydrogen plasma

International Nuclear Information System (INIS)

Gallegos, O.; Garcia, R.; Estrada, M.; Cerdeira, A.; Leyva, A.

2001-01-01

Poly-silicon thin film transistors (TFTs) are widely applied in integrated LCD driving circuits and image sensors, because they have better characteristics than a-Si:H TFTs. Poly-silicon can deposited or obtained by crystallization of amorphous silicon layers after annealing above 900 oC. For the last years, research is been done in order to crystallize a- Si:H films at low temperature and time budget. In this work we present crystallization at 650 oC of intrinsic and doped a-Si:H layers after a hydrogen plasma annealing to enhanced the crystallization process. Intrinsic layers crystallized in 4-6 hours after annealing in hydrogen plasma, while doped layers crystallized for the same annealing times, independently of been or not annealed in hydrogen plasma. Layers were characterized by XRD and by resistivity measurements. Resistivity of n-type layers changed from 300 to 0.02 cm after crystallization. Resistivity of i-layers also decreased, but both values are very high and it is difficult to determine with precision its change. The high resistivity of the polycrystalline layers is determined by the small grain size. Poly-silicon TFTs were fabricated using the above procedure to crystallize the amorphous layers. The complete fabrication process is presented. Output characteristics are shown and compared to same characteristics for a-Si:H TFTs fabricated simultaneously with the exception of the crystallization process. TFTs' sensibility to light was also used to verify that crystallization took place

Long-Term Stability of Oxide Nanowire Sensors via Heavily Doped Oxide Contact.

Science.gov (United States)

Zeng, Hao; Takahashi, Tsunaki; Kanai, Masaki; Zhang, Guozhu; He, Yong; Nagashima, Kazuki; Yanagida, Takeshi

2017-12-22

Long-term stability of a chemical sensor is an essential quality for long-term collection of data related to exhaled breath, environmental air, and other sources in the Internet of things (IoT) era. Although an oxide nanowire sensor has shown great potential as a chemical sensor, the long-term stability of sensitivity has not been realized yet due to electrical degradation under harsh sensing conditions. Here, we report a rational concept to accomplish long-term electrical stability of metal oxide nanowire sensors via introduction of a heavily doped metal oxide contact layer. Antimony-doped SnO 2 (ATO) contacts on SnO 2 nanowires show much more stable and lower electrical contact resistance than conventional Ti contacts for high temperature (200 °C) conditions, which are required to operate chemical sensors. The stable and low contact resistance of ATO was confirmed for at least 1960 h under 200 °C in open air. This heavily doped oxide contact enables us to realize the long-term stability of SnO 2 nanowire sensors while maintaining the sensitivity for both NO 2 gas and light (photo) detections. The applicability of our method is confirmed for sensors on a flexible polyethylene naphthalate (PEN) substrate. Since the proposed fundamental concept can be applied to various oxide nanostructures, it will give a foundation for designing long-term stable oxide nanomaterial-based IoT sensors.

Theoretical investigation of the heavily-doped semiconductor aspect of ultra-dilute GaAsN

Science.gov (United States)

Sukpitak, Jessada; Sa-yakanit, Virulh

2015-12-01

The model of GaAs1- y N y ( y = 0.001) as a heavily-doped semiconductor in the ultra-dilute region is attentively examined. The model enables GaAsN to be viewed as a disordered assembly of three-dimensional quantum dots (potential wells) caused by random potential fluctuations from nitrogen pairs in the system. Consequently, Feynman's path-integration technique is applied in order to quantify the density of states (DOS) in the vicinity of the conduction band edge. The obtained DOS tail, even though overestimated, still clearly shows a much shorter tail than that the experimental result does. This shows that the heavily-doped semiconductor viewpoint is not proper for GaAsN, not even in the ultra-dilute region. Furthermore, this also suggests that the impurity wave function overlap is not a basic mechanism of band gap reduction.

Backward diodes using heavily Mg-doped GaN growth by ammonia molecular-beam epitaxy

Science.gov (United States)

Okumura, Hironori; Martin, Denis; Malinverni, Marco; Grandjean, Nicolas

2016-02-01

We grew heavily Mg-doped GaN using ammonia molecular-beam epitaxy. The use of low growth temperature (740 °C) allows decreasing the incorporation of donor-like defects (p-type doping compensation. As a result, a net acceptor concentration of 7 × 1019 cm-3 was achieved, and the hole concentration measured by Hall effect was as high as 2 × 1019 cm-3 at room temperature. Using such a high Mg doping level, we fabricated GaN backward diodes without polarization-assisted tunneling. The backward diodes exhibited a tunneling-current density of 225 A/cm2 at a reverse bias of -1 V at room temperature.

One unit-cell seed layer induced epitaxial growth of heavily nitrogen doped anatase TiO{sub 2} films

Energy Technology Data Exchange (ETDEWEB)

Chen, T L; Hirose, Y; Hitosugi, T; Hasegawa, T [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan)], E-mail: chen@ksp.or.jp

2008-03-21

We present a novel way to obtain heavily nitrogen doped anatase TiO{sub 2} films by using a solid-state nitrogen source. Epitaxial growth of the films was realized by introducing one unit-cell seed layer, which was indicated by reflection high-energy electron diffraction as intensity oscillation. Results of x-ray diffraction and x-ray photoelectron spectroscopy confirmed that the films were in the anatase phase heavily doped with nitrogen of {approx}15 at%. The films obtained exhibited considerable narrowing of the optical bandgap, resulting in an enhancement of absorption in the visible-light region. (fast track communication)

Improvement on p-type CVD diamond semiconducting properties by fabricating thin heavily-boron-doped multi-layer clusters isolated each other in unintentionally boron-doped diamond layer

Science.gov (United States)

Maida, Osamu; Tabuchi, Tomohiro; Ito, Toshimichi

2017-12-01

We have developed a new fabrication process to decrease the effective activation energy of B atoms doped in diamond without a significant decrease in the carrier mobility by fabricating heavily B-doped clusters with very low mobility which are embedded in lightly-B-doped diamond layers. The resistivities of the heavily B-doped and unintentionally B-doped diamond stacked layers had almost no temperature dependence, suggesting the presence of an impurity-band conduction in these diamond layers. On the other hand, the resistivities of the samples after the embedding growth process of the stacked layers that had been appropriately divided to innumerable small clusters by means of a suitable etching process increased with decreasing the temperature from 330 to 130 K. The effective activation energies and Hall mobilities at room temperature of both samples were estimated to be 0.21 eV, 106 cm2 V-1 s-1 for micron-sized clusters and 0.23 eV, 470 cm2 V-1 s-1 for nano-sized clusters, respectively, indicating that the diamond film structure fabricated in this work is effective for the improvement of the p-type performance for the B-doped CVD diamond.

High-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga,Fe)Sb

International Nuclear Information System (INIS)

Tu, Nguyen Thanh; Hai, Pham Nam; Anh, Le Duc; Tanaka, Masaaki

2016-01-01

We show high-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga_1_−_x,Fe_x)Sb (x = 23% and 25%) thin films grown by low-temperature molecular beam epitaxy. Magnetic circular dichroism spectroscopy and anomalous Hall effect measurements indicate intrinsic ferromagnetism of these samples. The Curie temperature reaches 300 K and 340 K for x = 23% and 25%, respectively, which are the highest values reported so far in intrinsic III-V ferromagnetic semiconductors.

High-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga,Fe)Sb

Energy Technology Data Exchange (ETDEWEB)

Tu, Nguyen Thanh [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Department of Physics, Ho Chi Minh City University of Pedagogy, 280, An Duong Vuong Street, District 5, Ho Chi Minh City 748242 (Viet Nam); Hai, Pham Nam [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-0033 (Japan); Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Anh, Le Duc [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Tanaka, Masaaki [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

2016-05-09

We show high-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga{sub 1−x},Fe{sub x})Sb (x = 23% and 25%) thin films grown by low-temperature molecular beam epitaxy. Magnetic circular dichroism spectroscopy and anomalous Hall effect measurements indicate intrinsic ferromagnetism of these samples. The Curie temperature reaches 300 K and 340 K for x = 23% and 25%, respectively, which are the highest values reported so far in intrinsic III-V ferromagnetic semiconductors.

Heavily doped n-type a-IGZO by F plasma treatment and its thermal stability up to 600 °C

Science.gov (United States)

Um, Jae Gwang; Jang, Jin

2018-04-01

We report the electrical properties and thermal stability of heavily doped, amorphous indium-gallium-zinc-oxide (a-IGZO) treated with fluorine (F) plasma. When the F doping concentration in a-IGZO is 17.51 × 1021/cm-3, the a-IGZO exhibits a carrier concentration of 6 × 1019 cm-3, a resistivity of 3 × 10-3 Ω cm, and a Hall mobility of 20 cm2/V s. This indicates that F is a suitable n-type dopant in a-IGZO. The similarity of the ionic radius of F to that of oxygen (O) allows substitutional doping by replacing O with F or the occupation of the oxygen vacancy (VO) site by F and consequent reduction in defect density. The semiconducting property of a-IGZO can change into metallic behavior by F doping. The defect passivation by F incorporation is confirmed by the XPS depth profile, which reveals the significant reduction in the VO concentration due to the formation of In-F bonds. The heavily doped a-IGZO exhibits thermally stable conductivity up to 600 °C annealing and thus can be widely used for the ohmic contact of a-IGZO devices.

Sensitivity enhancement of polysilicon piezo-resistive pressure sensors with phosphorous diffused resistors

International Nuclear Information System (INIS)

Sivakumar, K; Dasgupta, N; Bhat, K N; Natarajan, K

2006-01-01

It is generally accepted that the piezo-resistive coefficient in single crystal silicon is higher when P-type impurities such as boron are used for doping the resistors. In this paper we demonstrate that the sensitivity of polycrystalline silicon piezo-resistive pressure sensors can be enhanced considerably when phosphorus diffusion source is used instead of boron dopant for realizing the piezo-resistors. Pressure sensors have been designed and fabricated with the polycrystalline piezo-resistors connected in the form of a Wheatstone bridge and laid out on thermal oxide grown on membranes obtained with a Silicon On Insulator (SOI) approach. The SOI wafers required for this purpose have been realized in-house by Silicon Fusion Bonding (SFB) and etch back technique in our laboratory. This approach provides excellent isolation between the resistors and enables zero temperature coefficient of the polysilicon resistor. The results obtained in our laboratory have clearly demonstrated that by optimizing the phosphorus diffusion temperature and duration, it is possible to achieve sensitivities in excess of 20mV /Bar for bridge input voltage of 10V, with linearity within 1% over a differential pressure range up to 10Bar (10 6 Pascal), and burst pressure in excess of 50 Bar as compared to the 10mV /Bar sensitivity obtained with boron doped polysilicon piezo-resistors. This enhancement is attributed to grain boundary passivation by phosphorous atoms

Einstein's photoemission emission from heavily-doped quantized structures

CERN Document Server

Ghatak, Kamakhya Prasad

2015-01-01

This monograph solely investigates the Einstein's Photoemission(EP) from Heavily Doped(HD) Quantized Structures on the basis of newly formulated electron dispersion laws. The materials considered are quantized structures of HD non-linear optical, III-V, II-VI, Ge, Te, Platinum Antimonide, stressed materials, GaP, Gallium Antimonide, II-V, Bismuth Telluride together with various types of HD superlattices and their Quantized counterparts respectively. The EP in HD opto-electronic materials and their nanostructures is studied in the presence of strong light waves and intense electric fields  that control the studies of such quantum effect devices. The suggestions for the experimental determinations of different important physical quantities in HD 2D and 3D materials  and the importance of measurement of band gap in HD optoelectronic materials under intense built-in electric field in nano devices and strong external photo excitation (for measuring   physical properties in the presence of intense light waves w...

Soft X-ray angle-resolved photoemission spectroscopy of heavily boron-doped superconducting diamond films

Directory of Open Access Journals (Sweden)

T. Yokoya, T. Nakamura, T. Matushita, T. Muro, H. Okazaki, M. Arita, K. Shimada, H. Namatame, M. Taniguchi, Y. Takano, M. Nagao, T. Takenouchi, H. Kawarada and T. Oguchi

2006-01-01

Full Text Available We have performed soft X-ray angle-resolved photoemission spectroscopy (SXARPES of microwave plasma-assisted chemical vapor deposition diamond films with different B concentrations in order to study the origin of the metallic behavior of superconducting diamond. SXARPES results clearly show valence band dispersions with a bandwidth of ~23 eV and with a top of the valence band at gamma point in the Brillouin zone, which are consistent with the calculated valence band dispersions of pure diamond. Boron concentration-dependent band dispersions near the Fermi level (EF exhibit a systematic shift of EF, indicating depopulation of electrons due to hole doping. These SXARPES results indicate that diamond bands retain for heavy boron doping and holes in the diamond band are responsible for the metallic states leading to superconductivity at low temperature. A high-resolution photoemission spectroscopy spectrum near EF of a heavily boron-doped diamond superconductor is also presented.

Near-Field Imaging of Free Carriers in ZnO Nanowires with a Scanning Probe Tip Made of Heavily Doped Germanium

Science.gov (United States)

Sakat, Emilie; Giliberti, Valeria; Bollani, Monica; Notargiacomo, Andrea; Pea, Marialilia; Finazzi, Marco; Pellegrini, Giovanni; Hugonin, Jean-Paul; Weber-Bargioni, Alexander; Melli, Mauro; Sassolini, Simone; Cabrini, Stefano; Biagioni, Paolo; Ortolani, Michele; Baldassarre, Leonetta

2017-11-01

A novel scanning probe tip made of heavily doped semiconductor is fabricated and used instead of standard gold-coated tips in infrared scattering-type near-field microscopy. Midinfrared near-field microscopy experiments are conducted on ZnO nanowires with a lateral resolution better than 100 nm, using tips made of heavily electron-doped germanium with a plasma frequency in the midinfrared (plasma wavelength of 9.5 μ m ). Nanowires embedded in a dielectric matrix are imaged at two wavelengths, 11.3 and 8.0 μ m , above and below the plasma wavelength of the tips. An opposite sign of the imaging contrasts between the nanowire and the dielectric matrix is observed at the two infrared wavelengths, indicating a clear role of the free-electron plasma in the heavily doped germanium tip in building the imaging contrast. Electromagnetic simulations with a multispherical dipole model accounting for the finite size of the tip are well consistent with the experiments. By comparison of the simulated and measured imaging contrasts, an estimate for the local free-carrier density in the investigated ZnO nanowires in the low 1019 cm-3 range is retrieved. The results are benchmarked against the scattering intensity and phase maps obtained on the same sample with a gold-coated probe tip in pseudoheterodyne detection mode.

Multi-layer enhancement to polysilicon surface-micromachining technology

Energy Technology Data Exchange (ETDEWEB)

Sniegowski, J.J.; Rodgers, M.S. [Sandia National Labs., Albuquerque, NM (United States). Intelligent Micromachine Dept.

1997-10-01

A multi-level polysilicon surface-micromachining technology consisting of 5 layers of polysilicon is presented. Surface topography and film mechanical stress are the major impediments encountered in the development of a multilayer surface-micromachining process. However, excellent mechanical film characteristics have been obtained through the use of chemical-mechanical polishing for planarization of topography and by proper sequencing of film deposition with thermal anneals. Examples of operating microactuators, geared power-transfer mechanisms, and optical elements demonstrate the mechanical advantages of construction with 5 polysilicon layers.

Design, Modeling, Fabrication, and Evaluation of Thermoelectric Generators with Hot-Wire Chemical Vapor Deposited Polysilicon as Thermoelement Material

Science.gov (United States)

de Leon, Maria Theresa; Tarazona, Antulio; Chong, Harold; Kraft, Michael

2014-11-01

This paper presents the design, modeling, fabrication, and evaluation of thermoelectric generators (TEGs) with p-type polysilicon deposited by hot-wire chemical vapor deposition (HWCVD) as thermoelement material. A thermal model is developed based on energy balance and heat transfer equations using lumped thermal conductances. Several test structures were fabricated to allow characterization of the boron-doped polysilicon material deposited by HWCVD. The film was found to be electrically active without any post-deposition annealing. Based on the tests performed on the test structures, it is determined that the Seebeck coefficient, thermal conductivity, and electrical resistivity of the HWCVD polysilicon are 113 μV/K, 126 W/mK, and 3.58 × 10-5 Ω m, respectively. Results from laser tests performed on the fabricated TEG are in good agreement with the thermal model. The temperature values derived from the thermal model are within 2.8% of the measured temperature values. For a 1-W laser input, an open-circuit voltage and output power of 247 mV and 347 nW, respectively, were generated. This translates to a temperature difference of 63°C across the thermoelements. This paper demonstrates that HWCVD, which is a cost-effective way of producing solar cells, can also be applied in the production of TEGs. By establishing that HWCVD polysilicon can be an effective thermoelectric material, further work on developing photovoltaic-thermoelectric (PV-TE) hybrid microsystems that are cost-effective and better performing can be explored.

Influence of quantum confinement on the carrier contribution to the elastic constants in quantum confined heavily doped non-linear optical and optoelectronic materials: simplified theory and the suggestion for experimental determination

International Nuclear Information System (INIS)

Baruah, D; Choudhury, S; Singh, K M; Ghatak, K P

2007-01-01

In this paper we study the carrier contribution to elastic constants in quantum confined heavily doped non-linear optical compounds on the basis of a newly formulated electron dispersion law taking into account the anisotropies of the effective electron masses and spin orbit splitting constants together with the proper inclusion of the crystal field splitting in the Hamiltonian within the framework of k.p formalism. All the results of heavily doped three, and two models of Kane for heavily doped III-V materials form special cases of our generalized analysis. It has been found, taking different heavily doped quantum confined materials that, the carrier contribution to the elastic constants increases with increase in electron statistics and decrease in film thickness in ladder like manners for all types of quantum confinements with different numerical values which are totally dependent on the energy band constants. The said contribution is greatest in quantum dots and least in quantum wells together with the fact the heavy doping enhances the said contributions for all types of quantum confined materials. We have suggested an experimental method of determining the carrier contribution to the elastic constants in nanostructured materials having arbitrary band structures

Features of the band structure and conduction mechanisms of n-HfNiSn heavily doped with Y

Energy Technology Data Exchange (ETDEWEB)

Romaka, V. A., E-mail: vromaka@polynet.lviv.ua [National Academy of Sciences of Ukraine, Pidstryhach Institute for Applied Problems of Mechanics and Mathematics (Ukraine); Rogl, P. [Universitet Wien, Institut für Physikalische Chemie (Austria); Romaka, V. V. [National University “Lvivska Politechnika” (Ukraine); Kaczorowski, D. [Polish Academy of Sciences, Institute of Low Temperature and Structure Research (Poland); Krayovskyy, V. Ya. [National University “Lvivska Politechnika” (Ukraine); Stadnyk, Yu. V.; Horyn, A. M. [Ivan Franko Lviv National University (Ukraine)

2017-02-15

The crystalline and electronic structures, energy, kinetic, and magnetic characteristics of n-HfNiSn semiconductor heavily doped with Y acceptor impurity are studied in the ranges: T = 80–400 K, N{sub A}{sup Y} ≈ 1.9 × 10{sup 20}–5.7 × 10{sup 21} cm{sup –3} (x = 0.01–0.30), and H ≤ 10 kG. The nature of the mechanism of structural defect generation is determined, which leads to a change in the band gap and the degree of semiconductor compensation, the essence of which is the simultaneous reduction and elimination of structural donor-type defects as a result of the displacement of ~1% of Ni atoms from the Hf (4a) site, and the generation of structural acceptor-type defects by substituting Hf atoms with Y atoms at the 4a site. The results of calculations of the electronic structure of Hf{sub 1–x}Y{sub x}NiSn are in agreement with the experimental data. The discussion is performed within the Shklovskii–Efros model of a heavily doped and compensated semiconductor.

Measurement of surface recombination velocity on heavily doped indium phosphide

International Nuclear Information System (INIS)

Jenkins, P.; Ghalla-Goradia, M.; Faur, M.; Bailey, S.

1990-01-01

The controversy surrounding the published low values of surface recombination velocity (SRV) in n-InP, solidified in recent years when modeling of existing n/p InP solar cells revealed that the front surface SRV had to be higher than 1 x 10 6 cm/sec in order to justify the poor blue response that is characteristic of all n/p InP solar cells. In this paper, SRV on heavily doped (>10 18 cm -3 )n-type and p-type InP is measured as a function of surface treatment. For the limited range of substrates and surface treatments studied, SRV and surface stability depend strongly on the surface treatment. SRVs of ∼10 5 cm/sec in both p-type and n-type InP are obtainable, but in n-type the low SRV surfaces were unstable, and the only stable surfaces on n-type had SRVs of >10 6 cm/sec

Heavily-doped 2D-quantized structures and the Einstein relation

CERN Document Server

Ghatak, Kamakhya P

2015-01-01

This book presents the Einstein Relation(ER) in two-dimensional (2-D) Heavily Doped(HD) Quantized Structures. The materials considered are quantized structures of HD non-linear optical, III-V, II-VI, Ge, Te, Platinum Antimonide, stressed materials, GaP, Gallium Antimonide, II-V, Bismuth Telluride together with various types of HD superlattices and their Quantized counterparts respectively. The ER in HD opto-electronic materials and their nanostructures is studied in the presence of strong light waves and intense electric fields on the basis of newly formulated electron dispersion laws that control the studies of such quantum effect devices. The suggestion for the experimental determination of HD 2D and 3D ERs and the importance of measurement of band gap in HD optoelectronic materials under intense built-in electric field in nanodevices and strong external photo excitation (for measuring photon induced physical properties) are also discussed in this context. The influence of crossed electric and quantizing ma...

Anomalous transmission through heavily doped conducting polymer films with periodic subwavelength hole array

Science.gov (United States)

Matsui, Tatsunosuke; Vardeny, Z. Valy; Agrawal, Amit; Nahata, Ajay; Menon, Reghu

2006-08-01

We observed resonantly enhanced (or anomalous transmission) terahertz transmission through two-dimensional (2D) periodic arrays of subwavelength apertures with various periodicities fabricated on metallic organic conducting polymer films of polypyrrole heavily doped with PF 6 molecules [PPy(PF6)]. The anomalous transmission spectra are in good agreement with a model involving surface plasmon polariton excitations on the film surfaces. We also found that the resonantly enhanced transmission peaks are broader in the exotic metallic PPy(PF6) films compared to those formed in 2D aperture array in regular metallic films such as silver, indicating that the surface plasmon polaritons on the PPy(PF6) film surfaces have higher attenuation.

Prospective high thermoelectric performance of the heavily p-doped half-Heusler compound CoVSn

International Nuclear Information System (INIS)

Shi, Hongliang; Ming, Wenmei; Parker, David S.; Du, Mao-Hua; Singh, David J.

2017-01-01

The electronic structure and transport properties of the half-Heusler compound CoVSn are studied in this paper systematically by combining first-principles electronic structure calculations and Boltzmann transport theory. The band structure at the valence-band edge is complex with multiple maxima derived from hybridized transition element d states. The result is a calculated thermopower larger than 200 μV /Κ within a wide range of doping concentrations and temperatures for heavily doped p-type CoVSn. The thermoelectric properties additionally benefit from the corrugated shapes of the hole pockets in our calculated isoenergy surfaces. Our calculated power factor S"2σ/τ (with respect to an average unknown scattering time) of CoVSn is comparable to that of FeNbSb. A smaller lattice thermal conductivity can be expected from the smaller group velocities of acoustical modes compared to FeNbSb. Finally, overall, good thermoelectric performance for CoVSn can be expected by considering the electronic transport and lattice thermal conductivity.

Comparison of the Thermal Degradation of Heavily Nb-Doped and Normal PZT Thin Films.

Science.gov (United States)

Yang, Jeong-Suong; Kang, YunSung; Kang, Inyoung; Lim, SeungMo; Shin, Seung-Joo; Lee, JungWon; Hur, Kang Heon

2017-03-01

The degradation of niobium-doped lead zirconate titanate (PZT) and two types of PZT thin films were investigated. Undoped PZT, two-step PZT, and heavily Nb-doped PZT (PNZT) around the morphotropic phase boundary were in situ deposited under optimum condition by RF-magnetron sputtering. All 2- [Formula: see text]-thick films had dense perovskite columnar grain structure and self-polarized (100) dominant orientation. PZT thin films were deposited on Pt/TiO x bottom electrode on Si wafer, and PNZT thin film was on Ir/TiW electrode with the help of orientation control. Sputtered PZT films formed on microelectromechanical system (MEMS) gyroscope and the degradation rates were compared at different temperatures. PNZT showed the best resistance to the thermal degradation, followed by two-step PZT. To clarify the effect of oxygen vacancies on the degradation of the film at high temperature, photoluminescence measurement was conducted, which confirmed that oxygen vacancy rate was the lowest in heavy PNZT. Nb-doping PZT thin films suppressed the oxygen deficit and made high imprint with self-polarization. This defect distribution and high internal field allowed PNZT thin film to make the piezoelectric sensors more stable and reliable at high temperature, such as reflow process of MEMS packaging.

Effect of impurity correlation on the density of states in slightly compensated heavily doped semiconductors

International Nuclear Information System (INIS)

Doan Nhat Quang; Nguyen Nhu Dat; Dinh Van An

1993-07-01

A theory is developed of the electron density of states (DOS) in slightly compensated heavily doped semiconductors which undergo a thermal treatment. The calculation is carried out within the semiclassical approach to the random impurity field, taking adequately into account high-temperature correlation among the impurities and low temperature screening due to the free carriers as well. Then, a simple analytic expression for the DOS is obtained which exhibits the same energy dependence as in the case of a random impurity distribution, but now with some correlation-induced changes in the coefficients. A numerical estimation on non-compensated n-type sample of GaAs at a doping level of 5 x 10 18 cm -3 shows that in the tail region the correlated DOS turns out to be somewhat larger and cut less sharply than the random one. (author). 45 refs, 2 figs, 1 tab

PULSION registered HP: Tunable, High Productivity Plasma Doping

International Nuclear Information System (INIS)

Felch, S. B.; Torregrosa, F.; Etienne, H.; Spiegel, Y.; Roux, L.; Turnbaugh, D.

2011-01-01

Plasma doping has been explored for many implant applications for over two decades and is now being used in semiconductor manufacturing for two applications: DRAM polysilicon counter-doping and contact doping. The PULSION HP is a new plasma doping tool developed by Ion Beam Services for high-volume production that enables customer control of the dominant mechanism--deposition, implant, or etch. The key features of this tool are a proprietary, remote RF plasma source that enables a high density plasma with low chamber pressure, resulting in a wide process space, and special chamber and wafer electrode designs that optimize doping uniformity.

Topology optimized electrothermal polysilicon microgrippers

DEFF Research Database (Denmark)

Sardan Sukas, Özlem; Petersen, Dirch Hjorth; Mølhave, Kristian

2008-01-01

This paper presents the topology optimized design procedure and fabrication of electrothermal polysilicon microgrippers for nanomanipulation purposes. Performance of the optimized microactuators is compared with a conventional three-beam microactuator design through finite element analysis...

Author Details

African Journals Online (AJOL)

Abadli, S. Vol 18 (2006) - Articles Growth of grains effect on boron diffusion in heavily doped LPCVD polysilicon thin films. Abstract · Vol 17 (2005) - Articles Cinetique de croissance et de dissolution des clusters et effet des tres forts dopages sur la diffusion du dopant dans des films minces de polysilicium. Abstract.

Effects of thin heavily Mg-doped GaN capping layer on ohmic contact formation of p-type GaN

International Nuclear Information System (INIS)

Wu, L L; Zhao, D G; Jiang, D S; Chen, P; Le, L C; Li, L; Liu, Z S; Zhang, S M; Zhu, J J; Wang, H; Zhang, B S; Yang, H

2013-01-01

The growth condition of thin heavily Mg-doped GaN capping layer and its effect on ohmic contact formation of p-type GaN were investigated. It is confirmed that the excessive Mg doping can effectively enhance the Ni/Au contact to p-GaN after annealing at 550 °C. When the flow rate ratio between Mg and Ga gas sources is 6.4% and the layer width is 25 nm, the capping layer grown at 850 °C exhibits the best ohmic contact properties with respect to the specific contact resistivity (ρ c ). This temperature is much lower than the conventional growth temperature of Mg-doped GaN, suggesting that the deep-level-defect induced band may play an important role in the conduction of capping layer. (paper)

Thermal conductivity of high-porosity heavily doped biomorphic silicon carbide prepared from sapele wood biocarbon

Science.gov (United States)

Parfen'eva, L. S.; Orlova, T. S.; Smirnov, B. I.; Smirnov, I. A.; Misiorek, H.; Mucha, J.; Jezowski, A.; Cabezas-Rodriguez, R.; Ramirez-Rico, J.

2012-08-01

The electrical resistivity and thermal conductivity of high-porosity (˜52 vol %, channel-type pores) bio-SiC samples prepared from sapele wood biocarbon templates have been measured in the temperature range 5-300 K. An analysis has been made of the obtained results in comparison with the data for bio-SiC samples based on beech and eucalyptus, as well as for polycrystalline β-SiC. The conclusion has been drawn that the electrical resistivity and thermal conductivity of bio-SiC samples based on natural wood are typical of heavily doped polycrystalline β-SiC.

High Thermoelectric Performance by Convergence of Bands in IV-VI Semiconductors, Heavily Doped PbTe, and Alloys/Nanocomposites

Science.gov (United States)

Snyder, G. Jeffrey (Inventor); Pei, Yanzhong (Inventor)

2015-01-01

The present invention teaches an effective mechanism for enhancing thermoelectric performance through additional conductive bands. Using heavily doped p-PbTe materials as an example, a quantitative explanation is disclosed, as to why and how these additional bands affect the figure of merit. A high zT of approaching 2 at high temperatures makes these simple, likely more stable (than nanostructured materials) and Tl-free materials excellent for thermoelectric applications.

Carrier compensation mechanism in heavily Nb-doped anatase Ti{sub 1-x}Nb{sub x}O{sub 2+{delta}} epitaxial thin films

Energy Technology Data Exchange (ETDEWEB)

Nogawa, H; Chikamatsu, A; Hirose, Y; Hasegawa, T [Department of Chemistry, University of Tokyo, Tokyo 113-0033 (Japan); Nakao, S [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Kumigashira, H; Oshima, M, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp [Department of Applied Chemistry, University of Tokyo, Tokyo 113-8656 (Japan)

2011-09-14

We investigated the electronic structures of anatase Ti{sub 1-x}Nb{sub x}O{sub 2+{delta}} (TNO) thin films as a function of Nb concentration x using photoemission spectroscopy (PES) measurements to elucidate the origin of the abrupt decrease in carrier activation in heavily Nb-doped regime. The existing intensity ratio of Nb{sup 5+} evaluated from Nb 3d core-level PES spectra maintained a constant value of {approx}0.8 at x = 0.06-0.3, implying that electron carriers generated by Nb doping are compensated by p-type defects. Ti 2p-3d and O1s-2p resonant PES measurements of x = 0.06-0.3 films revealed that the in-gap states positioned {approx}1 eV below the Fermi level (E{sub F}) have a mixed character of Ti 3d and O 2p orbitals, whereas the states at E{sub F} mainly have a Ti 3d nature. We proposed a carrier compensation mechanism that interstitial oxygen atoms strongly combined with surrounding Nb atoms kill conduction electrons in heavily Nb-doped anatase TiO{sub 2}.

Optimization of nitridation conditions for high quality inter-polysilicon dielectric layers

NARCIS (Netherlands)

Klootwijk, J.H.; Bergveld, H.J.; van Kranenburg, H.; Woerlee, P.H.; Wallinga, Hans

1996-01-01

Nitridation of deposited high temperature oxides (HTO) was studied to form high quality inter-polysilicon dielectric layers for embedded non volatile memories. Good quality dielectric layers were obtained earlier by using an optimized deposition of polysilicon and by performing a post-dielectric

Highly efficient and heavily-doped organic light-emitting devices based on an orange phosphorescent iridium complex

International Nuclear Information System (INIS)

Zhou, Shunliang; Wang, Qi; Li, Ming; Lu, Zhiyun; Yu, Junsheng

2014-01-01

Heavily doped and highly efficient phosphorescent organic light-emitting devices (PhOLEDs) had been fabricated by utilizing an orange iridium complex, bis[2-(3′,5′-di-tert-butylbiphenyl-4-yl)benzothiazolato-N,C 2' ]iridium(III) (acetylacetonate) [(tbpbt) 2 Ir(acac)], as a phosphor. When the doping concentration of [(tbpbt) 2 Ir(acac)] reached as high as 15 wt%, the PhOLEDs exhibited a power efficiency, current efficiency, and external quantum efficiency of 24.5 lm/W, 32.1 cd/A, 15.7%, respectively, implying a promising quenching-resistant characteristics of this novel phosphor. Furthermore, the efficient white PhOLEDs had been obtained by employing (tbpbt) 2 Ir(acac) as a self-host orange emitter, indicating that (tbpbt) 2 Ir(acac) could serve as a promising phosphor to fabricate white organic light-emitting devices with simplified manufacturing process. - Highlights: • Efficient phosphorescent devices were fabricated. • Optimized phosphor doping ratio reached as high as 15 wt%. • The results proved a promising quench-resistant property of the phosphor. • Efficient white devices based on this phosphor as self-host layer had been realized

Highly efficient and heavily-doped organic light-emitting devices based on an orange phosphorescent iridium complex

Energy Technology Data Exchange (ETDEWEB)

Zhou, Shunliang; Wang, Qi [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China); Li, Ming [College of Chemistry, Sichuan University, Chengdu, 610064 (China); Lu, Zhiyun, E-mail: luzhiyun@scu.edu.cn [College of Chemistry, Sichuan University, Chengdu, 610064 (China); Yu, Junsheng, E-mail: jsyu@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)

2014-10-15

Heavily doped and highly efficient phosphorescent organic light-emitting devices (PhOLEDs) had been fabricated by utilizing an orange iridium complex, bis[2-(3′,5′-di-tert-butylbiphenyl-4-yl)benzothiazolato-N,C{sup 2'}]iridium(III) (acetylacetonate) [(tbpbt){sub 2}Ir(acac)], as a phosphor. When the doping concentration of [(tbpbt){sub 2}Ir(acac)] reached as high as 15 wt%, the PhOLEDs exhibited a power efficiency, current efficiency, and external quantum efficiency of 24.5 lm/W, 32.1 cd/A, 15.7%, respectively, implying a promising quenching-resistant characteristics of this novel phosphor. Furthermore, the efficient white PhOLEDs had been obtained by employing (tbpbt){sub 2}Ir(acac) as a self-host orange emitter, indicating that (tbpbt){sub 2}Ir(acac) could serve as a promising phosphor to fabricate white organic light-emitting devices with simplified manufacturing process. - Highlights: • Efficient phosphorescent devices were fabricated. • Optimized phosphor doping ratio reached as high as 15 wt%. • The results proved a promising quench-resistant property of the phosphor. • Efficient white devices based on this phosphor as self-host layer had been realized.

High-efficiency and heavily doped organic light-emitting devices based on quench-resistant red iridium complex

Energy Technology Data Exchange (ETDEWEB)

Wang, Qi [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China); Yu, Junsheng, E-mail: jsyu@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China); Zhao, Juan; Wang, Jun [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China); Li, Ming [College of Chemistry, Sichuan University, Chengdu 610064 (China); Lu, Zhiyun, E-mail: luzhiyun@scu.edu.cn [College of Chemistry, Sichuan University, Chengdu 610064 (China)

2013-02-15

Highly efficient red phosphorescent organic light-emitting devices had been fabricated using a new iridium complex, bis[2-(9,9-dimethyl-9H-fluoren-2-yl) benzothiazolato-N,C{sup 2'}]iridium(III) (acetylacetonate) [(fbt){sub 2}Ir(acac)] as phosphor. With a high doping concentration of 15 wt%, the device exhibited a maximum luminance efficiency, power efficiency and external quantum efficiency (EQE) of 35.2 cd/A, 21.3 lm/W, 18.2%, respectively, indicating an excellent quench-resistant property of (fbt){sub 2}Ir(acac). The results are appealing towards the development of 'easy-to-make' OLEDs. It has been demonstrated that the high efficiency arises from more balanced charge carriers in the emissive layer. - Highlight: Black-Right-Pointing-Pointer We obtained efficient OLEDs based on newly synthesized quench-resistant phosphor. Black-Right-Pointing-Pointer Peak performance was obtained with 15 wt% (fbt){sub 2}Ir(acac) doped device. Black-Right-Pointing-Pointer Our devices gave one of the best performance among heavily-doped red devices. Black-Right-Pointing-Pointer Balanced carrier transport is crucial for the high performance of our devices.

Defects in heavily phosphorus-doped Si epitaxial films probed by monoenergetic positron beams

International Nuclear Information System (INIS)

Uedono, Akira; Tanigawa, Shoichiro; Suzuki, Ryoichi; Ohgaki, Hideaki; Mikado, Tomohisa.

1994-01-01

Vacancy-type defects in heavily phosphorus-doped Si epitaxial films were probed by monoenergetic positron beams. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured for the epitaxial films grown on the Si substrates by plasma chemical vapor deposition. For the as-deposited film, divacancy-phosphorus complexes were found with high concentration. After 600degC annealing, vacancy clusters were formed near the Si/Si interface, while no drastic change in the depth distribution of the divacancy-phosphorus complexes was observed. By 900degC annealing, the vacancy clusters were annealed out; however, the average number of phosphorus atoms coupled with divacancies increased. The relationship between the vacancy-type defects probed by the positron annihilation technique and the carrier concentration was confirmed. (author)

Defects in heavily phosphorus-doped Si epitaxial films probed by monoenergetic positron beams

Energy Technology Data Exchange (ETDEWEB)

Uedono, Akira; Tanigawa, Shoichiro [Tsukuba Univ., Ibaraki (Japan). Inst. of Materials Science; Suzuki, Ryoichi; Ohgaki, Hideaki; Mikado, Tomohisa

1994-11-01

Vacancy-type defects in heavily phosphorus-doped Si epitaxial films were probed by monoenergetic positron beams. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured for the epitaxial films grown on the Si substrates by plasma chemical vapor deposition. For the as-deposited film, divacancy-phosphorus complexes were found with high concentration. After 600degC annealing, vacancy clusters were formed near the Si/Si interface, while no drastic change in the depth distribution of the divacancy-phosphorus complexes was observed. By 900degC annealing, the vacancy clusters were annealed out; however, the average number of phosphorus atoms coupled with divacancies increased. The relationship between the vacancy-type defects probed by the positron annihilation technique and the carrier concentration was confirmed. (author).

Spin relaxation through lateral spin transport in heavily doped n -type silicon

Science.gov (United States)

Ishikawa, M.; Oka, T.; Fujita, Y.; Sugiyama, H.; Saito, Y.; Hamaya, K.

2017-03-01

We experimentally study temperature-dependent spin relaxation including lateral spin diffusion in heavily doped n -type silicon (n+-Si ) layers by measuring nonlocal magnetoresistance in small-sized CoFe/MgO/Si lateral spin-valve (LSV) devices. Even at room temperature, we observe large spin signals, 50-fold the magnitude of those in previous works on n+-Si . By measuring spin signals in LSVs with various center-to-center distances between contacts, we reliably evaluate the temperature-dependent spin diffusion length (λSi) and spin lifetime (τSi). We find that the temperature dependence of τSi is affected by that of the diffusion constant in the n+-Si layers, meaning that it is important to understand the temperature dependence of the channel mobility. A possible origin of the temperature dependence of τSi is discussed in terms of the recent theories by Dery and co-workers.

Influence of a deep-level-defect band formed in a heavily Mg-doped GaN contact layer on the Ni/Au contact to p-GaN

International Nuclear Information System (INIS)

Li Xiao-Jing; Zhao De-Gang; Jiang De-Sheng; Chen Ping; Zhu Jian-Jun; Liu Zong-Shun; Yang Jing; He Xiao-Guang; Yang Hui; Zhang Li-Qun; Zhang Shu-Ming; Le Ling-Cong; Liu Jian-Ping

2015-01-01

The influence of a deep-level-defect (DLD) band formed in a heavily Mg-doped GaN contact layer on the performance of Ni/Au contact to p-GaN is investigated. The thin heavily Mg-doped GaN (p ++ -GaN) contact layer with DLD band can effectively improve the performance of Ni/Au ohmic contact to p-GaN. The temperature-dependent I–V measurement shows that the variable-range hopping (VRH) transportation through the DLD band plays a dominant role in the ohmic contact. The thickness and Mg/Ga flow ratio of p ++ -GaN contact layer have a significant effect on ohmic contact by controlling the Mg impurity doping and the formation of a proper DLD band. When the thickness of the p ++ -GaN contact layer is 25 nm thick and the Mg/Ga flow rate ratio is 10.29%, an ohmic contact with low specific contact resistivity of 6.97× 10 −4 Ω·cm 2 is achieved. (paper)

Mobility and Device Applications of Heavily Doped Silicon and Strained SILICON(1-X) Germanium(x) Layers

Science.gov (United States)

Carns, Timothy Keith

With the advent of Si molecular beam epitaxy (Si -MBE), a significant amount of research has occurred to seek alternative high conductivity Si-based materials such as rm Si_{1-x}Ge_ {x} and delta-doped Si. These materials have brought improvements in device speeds and current drives with the added advantage of monolithic integration into Si VLSI circuits. The bulk of research in Si-based materials has been devoted to the implementation of strained rm Si_{1-x}Ge_{x} as the base layer of a rm Si_ {1-x}Ge_{x}/Si heterojunction bipolar transistor (HBT). Because of the valence band offset, the rm Si_{1-x}Ge _{x} layer can be heavily doped, leading to lower base sheet resistances and hence, improved speed performances. The Ge content in the base can also be graded to increase the drift field in the base. However, very few hole mobility measurements have been done in these strained layers, leading to limitations in device modeling and in understanding the transport behavior in this important material. In addition to rm Si_{1 -x}Ge_{x}, much potential also exists in using delta-doping in Si for improved conductivities over those of bulk Si. However, as of yet, delta-doped Si has received little attention. Therefore, this dissertation is dedicated to the investigation of both of these Si-based materials (strained rm Si_{1-x}Ge_{x } and delta-doped Si and rm Si_{1-x}Ge_ {x}) for the purpose of obtaining higher conductivities than comparably doped bulk Si. This work is divided into three parts to accomplish this objective. The first part is contained in Chapter 3 and is comprised of a comprehensive characterization of the hole mobility in compressively strained rm Si_{1 -x}Ge_{x}. Few results have been obtained prior to this research which has led to many inaccuracies in device modeling. The second part of this dissertation in Chapters 4 and 5 is devoted to the study of the mobility behavior in both boron and antimony delta-doped Si and rm Si_ {1-x}Ge_{x}. The important

Piezoresistive polysilicon film obtained by low-temperature aluminum-induced crystallization

International Nuclear Information System (INIS)

Patil, Suraj Kumar; Celik-Butler, Zeynep; Butler, Donald P.

2010-01-01

A low-temperature deposition process employing aluminum-induced crystallization has been developed for fabrication of piezoresistive polycrystalline silicon (polysilicon) films on low cost and flexible polyimide substrates for force and pressure sensing applications. To test the piezoresistive properties of the polysilicon films, prototype pressure sensors were fabricated on surface-micromachined silicon nitride (Si 3 N 4 ) diaphragms, in a half-Wheatstone bridge configuration. Characterization of the pressure sensor was performed using atomic force microscope in contact mode with a specially modified probe-tip. Low pressure values ranging from 5 kPa to 45 kPa were achieved by this method. The resistance change was found to be - 0.1% to 0.5% and 0.07% to 0.3% for polysilicon films obtained at 500 o C and 400 o C, respectively, for the applied pressure range.

Unusual near-band-edge photoluminescence at room temperature in heavily-doped ZnO:Al thin films prepared by pulsed laser deposition

International Nuclear Information System (INIS)

Mohanty, Bhaskar Chandra; Yeon, Deuk Ho; Das, Sachindra Nath; Kwak, Ji Hye; Yoon, Kyung Hoon; Cho, Yong Soo

2013-01-01

Room temperature photoluminescence (PL) properties of heavily-doped ZnO:Al thin films (with carrier concentration n in the range of 5–20 × 10 20 cm −3 ) prepared by pulsed laser deposition have been investigated. Despite their high carrier concentration, the films exhibited strong room temperature near-band-edge bound excitons at ∼3.34 eV and an unusual peak at ∼3.16 eV, and negligible deep-level emission even for the films deposited at a temperature as low as 25 °C. The radiative efficiency of the films increased with growth temperature as a result of increased n and improved crystallinity. A large blue shift of optical band gap was observed, which is consistent with the n-dependent Burstein–Moss and band gap-renormalization effects. Comparison of the results of the PL and optical measurements revealed a large Stokes shift that increased with increase in n. It has been explained by a model based on local potential fluctuations caused by randomly-distributed doping impurities. - Highlights: • Studied PL properties of heavily-doped ZnO:Al films grown by PLD. • Unusual strong near-band-edge emissions and negligible deep-level emission at RT. • Increased optical band gap with growth temperature and thus carrier concentration. • Stokes shift and PL peak width increased with carrier concentration. • Results explained by a model based on local potential fluctuations

Resonantly-enhanced transmission through a periodic array of subwavelength apertures in heavily-doped conducting polymer films

Science.gov (United States)

Matsui, Tatsunosuke; Vardeny, Z. Valy; Agrawal, Amit; Nahata, Ajay; Menon, Reghu

2006-02-01

We observed resonantly-enhanced terahertz transmission through two-dimensional (2D) periodic arrays of subwavelength apertures with various periodicities fabricated on metallic organic conducting polymer films of polypyrrole heavily doped with PF6 molecules [PPy(PF6)]. The "anomalous transmission" spectra are in good agreement with a model involving surface plasmon polariton excitations on the film surfaces. We also found that the `anomalous transmission' peaks are broader in the exotic metallic PPy (PF6) films compared to those formed in 2D aperture array in regular metallic films such as silver, showing that the surface plasmon polaritons on the PPy (PF6) film surfaces have higher attenuation.

High critical currents in heavily doped (Gd,Y)Ba2Cu3Ox superconductor tapes

Energy Technology Data Exchange (ETDEWEB)

Selvamanickam, V; Gharahcheshmeh, MH; Xu, A; Galstyan, E; Delgado, L; Cantoni, C

2015-01-19

REBa2Cu3Ox ((REBCO), RE = rare earth) superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50K and fields of 2-30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (J(c)) above 20 MA/cm(2) at 30 K, 3 T in heavily doped (25 mol.% Zr-added) (Gd,Y)Ba2Cu3Ox superconductor tapes, which is more than three times higher than the J(c) typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m(3) have also been attained at 20 K. A composition map of lift factor in J(c) (ratio of J(c) at 30 K, 3 T to the J(c) at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO3 (BZO) nanocolumn defect density of nearly 7 x 10(11) cm(-2) as well as 2-3 nm sized particles rich in Cu and Zr have been found in the high J(c) films. (C) 2015 AIP Publishing LLC.

Effect of Aluminum Doping on the Nanocrystalline ZnS:Al3+ Films Fabricated on Heavily-Doped p-type Si(100) Substrates by Chemical Bath Deposition Method

Science.gov (United States)

Zhu, He-Jie; Liang, Yan; Gao, Xiao-Yong; Guo, Rui-Fang; Ji, Qiang-Min

2015-06-01

Intrinsic ZnS and aluminum-doped nanocrystalline ZnS (ZnS:Al3+) films with zinc-blende structure were fabricated on heavily-doped p-type Si(100) substrates by chemical bath deposition method. Influence of aluminum doping on the microstructure, and photoluminescent and electrical properties of the films, were intensively investigated. The average crystallite size of the films varying in the range of about 9.0 ˜ 35.0 nm initially increases and then decreases with aluminum doping contents, indicating that the crystallization of the films are initially enhanced and then weakened. The incorporation of Al3+ was confirmed from energy dispersive spectrometry and the induced microstrain in the films. Strong and stable visible emission band resulting from the defect-related light emission were observed for the intrinsic ZnS and ZnS:Al3+ films at room temperature. The photoluminescence related to the aluminum can annihilate due to the self-absorption of ZnS:Al3+ when the Al3+ content surpasses certain value. The variation of the resistivity of the films that initially reduces and then increases is mainly caused by the partial substitute for Zn2+ by Al3+ as well as the enhanced crystallization, and by the enhanced crystal boundary scattering, respectively.

Defect formation in heavily doped Si upon irradiation

International Nuclear Information System (INIS)

Gubskaya, V.I.; Kuchinskii, P.V.; Lomako, V.M.

1981-01-01

The rates of the carrier removal and radiation defect introduction into n- and p-Si in the concentration range of 10 14 to 10 17 cm -3 upon 7-MeV-electron irradiation have been studied. The spectrum of the vacancy-type defects, defining the carrier removal rate in lightly doped crystals has been found. With doping level increase the carrier removal rate grows irrespective of conductivity type, and at n 0 , p 0 > 10 17 cm -3 is close to the total displacement number. At the same time a decrease in the introduction rate of the known vacancy-type defects is observed. x It is shown that a considerable growth of the carrier removal rate is defined neither by introduction of shallow compensating centers, nor by change in the primary defect charge state. It is suggested that at high doping impurity concentrations compensation in Si is due to the introduction of complexes doping impurity-interstitial or (impurity atom-interstitial) + vacancy, which give deep levels. (author)

Macrodesign for microdevices: Polysilicon surface-micromachining technology, applications and issues

Energy Technology Data Exchange (ETDEWEB)

Sniegowski, J.J. [Sandia National Labs., Albuquerque, NM (United States). Intelligent Micromachine Dept.

1997-05-01

The intent of this tutorial is to overview the technology of multi-level polysilicon surface micromachining, to present examples of devices which fully utilize this level of complexity, and to discuss what they believe to be significant issues which are not fully resolved. Following this intent, the tutorial consists of four sections. The first is an introduction and description of multi-level polysilicon surface micromachining and its potential benefits. Specifically, the inclusion of a third deposited layer of mechanical polysilicon greatly extends the degree of complexity available for micromechanism design. The second section introduces wafer planarization by CMP as a process tool for surface micromachining. The third section presents examples of actuated geared micromechanisms which require the multi-level fabrication process. Demonstration of actuation mechanisms coupled to external devices are illustrated. Finally, polysilicon surface micromachining fabrication technology has reached a level where many device designs, for the most part, can be embodied in the technology to produce a mechanical construct which provides the desired function. When designed properly, the fabricated mechanical element, if free to operate, will produce the desired function. However, one set of issues which can hinder or prevent operation are related to the post-fabricated device surfaces. These surface issues; namely, stiction, friction, and wear, are emphasized in the final section as a major hindrance to realizing the full potential of surface micromachined devices.

The effect of irradiation temperature on the optical attenuation recovery in heavily Ge-doped single mode silica core fibers

International Nuclear Information System (INIS)

Bertolotti, M.; Mabrouk, M.A.; Ferrari, A.; Serra, A.; Viezzoli, G.

1992-01-01

The behaviour under irradiation of a single mode fiber heavily doped with germanium has been investigated at 0.85 μm and 1.3 μm under different irradiation temperatures in the range from -65degC to 60degC. The time behaviour of the recovery of the induced attenuation has been described using empirical equations, for different temperatures. An nth order kinetics seems appropriate to describe the results and the order of kinetics has been determined at different temperatures. (orig.)

High critical currents in heavily doped (Gd,Y)Ba2Cu3Ox superconductor tapes

International Nuclear Information System (INIS)

Selvamanickam, V.; Gharahcheshmeh, M. Heydari; Xu, A.; Galstyan, E.; Delgado, L.; Cantoni, C.

2015-01-01

REBa 2 Cu 3 O x ((REBCO), RE = rare earth) superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50 K and fields of 2–30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (J c ) above 20 MA/cm 2 at 30 K, 3 T in heavily doped (25 mol. % Zr-added) (Gd,Y)Ba 2 Cu 3 O x superconductor tapes, which is more than three times higher than the J c typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m 3 have also been attained at 20 K. A composition map of lift factor in J c (ratio of J c at 30 K, 3 T to the J c at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO 3 (BZO) nanocolumn defect density of nearly 7 × 10 11  cm −2 as well as 2–3 nm sized particles rich in Cu and Zr have been found in the high J c films

Coplanar amorphous-indium-gallium-zinc-oxide thin film transistor with He plasma treated heavily doped layer

Energy Technology Data Exchange (ETDEWEB)

Jeong, Ho-young [Advanced Display Research Center, Department of Information Display, Kyung Hee University, Dongdaemun-gu, Seoul 130-701 (Korea, Republic of); LG Display R and D Center, 245 Lg-ro, Wollong-myeon, Paju-si, Gyeonggi-do 413-811 (Korea, Republic of); Lee, Bok-young; Lee, Young-jang; Lee, Jung-il; Yang, Myoung-su; Kang, In-byeong [LG Display R and D Center, 245 Lg-ro, Wollong-myeon, Paju-si, Gyeonggi-do 413-811 (Korea, Republic of); Mativenga, Mallory; Jang, Jin, E-mail: jjang@khu.ac.kr [Advanced Display Research Center, Department of Information Display, Kyung Hee University, Dongdaemun-gu, Seoul 130-701 (Korea, Republic of)

2014-01-13

We report thermally stable coplanar amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with heavily doped n{sup +} a-IGZO source/drain regions. Doping is through He plasma treatment in which the resistivity of the a-IGZO decreases from 2.98 Ω cm to 2.79 × 10{sup −3} Ω cm after treatment, and then it increases to 7.92 × 10{sup −2} Ω cm after annealing at 300 °C. From the analysis of X-ray photoelectron spectroscopy, the concentration of oxygen vacancies in He plasma treated n{sup +}a-IGZO does not change much after thermal annealing at 300 °C, indicating thermally stable n{sup +} a-IGZO, even for TFTs with channel length L = 4 μm. Field-effect mobility of the coplanar a-IGZO TFTs with He plasma treatment changes from 10.7 to 9.2 cm{sup 2}/V s after annealing at 300 °C, but the performance of the a-IGZO TFT with Ar or H{sub 2} plasma treatment degrades significantly after 300 °C annealing.

Coplanar amorphous-indium-gallium-zinc-oxide thin film transistor with He plasma treated heavily doped layer

International Nuclear Information System (INIS)

Jeong, Ho-young; Lee, Bok-young; Lee, Young-jang; Lee, Jung-il; Yang, Myoung-su; Kang, In-byeong; Mativenga, Mallory; Jang, Jin

2014-01-01

We report thermally stable coplanar amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with heavily doped n + a-IGZO source/drain regions. Doping is through He plasma treatment in which the resistivity of the a-IGZO decreases from 2.98 Ω cm to 2.79 × 10 −3 Ω cm after treatment, and then it increases to 7.92 × 10 −2 Ω cm after annealing at 300 °C. From the analysis of X-ray photoelectron spectroscopy, the concentration of oxygen vacancies in He plasma treated n + a-IGZO does not change much after thermal annealing at 300 °C, indicating thermally stable n + a-IGZO, even for TFTs with channel length L = 4 μm. Field-effect mobility of the coplanar a-IGZO TFTs with He plasma treatment changes from 10.7 to 9.2 cm 2 /V s after annealing at 300 °C, but the performance of the a-IGZO TFT with Ar or H 2 plasma treatment degrades significantly after 300 °C annealing

Path-integral calculation of the density of states in heavily doped strongly compensated semiconductors in a magnetic field

International Nuclear Information System (INIS)

Koinov, Z.G.; Yanchev, I.Y.

1981-09-01

The density of states in heavily doped strongly compansated semiconductors in a strong magnetic field is calculated by using the path-integral method. The case is considered when correlation exists in the impurity positions owing to the Coulomb interactions between the charged donors and acceptors during the high-temperature preparation of the samples. The semiclassical formula is rederived and corrections to it due to the long-range character of the potential and its short-range fluctuations are obtained. The density of states in the tail is studied and analytical results are given in the classical and quantum cases. (author)

Modeling Impact-induced Failure of Polysilicon MEMS: A Multi-scale Approach.

Science.gov (United States)

Mariani, Stefano; Ghisi, Aldo; Corigliano, Alberto; Zerbini, Sarah

2009-01-01

Failure of packaged polysilicon micro-electro-mechanical systems (MEMS) subjected to impacts involves phenomena occurring at several length-scales. In this paper we present a multi-scale finite element approach to properly allow for: (i) the propagation of stress waves inside the package; (ii) the dynamics of the whole MEMS; (iii) the spreading of micro-cracking in the failing part(s) of the sensor. Through Monte Carlo simulations, some effects of polysilicon micro-structure on the failure mode are elucidated.

Fabrication and characteristics of magnetic field sensors based on nano-polysilicon thin-film transistors

International Nuclear Information System (INIS)

Zhao Xiaofeng; Wen Dianzhong; Zhuang Cuicui; Cao Jingya; Wang Zhiqiang

2013-01-01

A magnetic field sensor based on nano-polysilicon thin films transistors (TFTs) with Hall probes is proposed. The magnetic field sensors are fabricated on 〈100〉 orientation high resistivity (ρ > 500 Ω·cm) silicon substrates by using CMOS technology, which adopt nano-polysilicon thin films with thicknesses of 90 nm and heterojunction interfaces between the nano-polysilicon thin films and the high resistivity silicon substrates as the sensing layers. The experimental results show that when V DS = 5.0 V, the magnetic sensitivities of magnetic field sensors based on nano-polysilicon TFTs with length—width ratios of 160 μm/80 μm, 320 μm/80 μm and 480 μm/80 μm are 78 mV/T, 55 mV/T and 34 mV/T, respectively. Under the same conditions, the magnetic sensitivity of the obtained magnetic field sensor is significantly improved in comparison with a Hall magnetic field sensor adopting silicon as the sensing layers. (semiconductor technology)

Heavily doped GaAs:Te layers grown by MOVPE using diisopropyl telluride as a source

Energy Technology Data Exchange (ETDEWEB)

Daniltsev, V. M.; Demidov, E. V.; Drozdov, M. N.; Drozdov, Yu. N., E-mail: drozdyu@ipmras.ru; Kraev, S. A.; Surovegina, E. A.; Shashkin, V. I.; Yunin, P. A. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

2016-11-15

The capabilities of GaAs epitaxial layers extremely heavily doped with tellurium by metal-organic vapor-phase epitaxy using diisopropyl telluride as a source are studied. It is shown that tellurium incorporation into GaAs occurs to an atomic concentration of 10{sup 21} cm{sup –3} without appreciable diffusion and segregation effects. Good carrier concentrations (2 × 10{sup 19} cm{sup –3}) and specific contact resistances of non-alloyed ohmic contacts (1.7 × 10{sup –6} Ω cm{sup 2}) give grounds to use such layers to create non-alloyed ohmic contacts in electronic devices. A sharp decrease in the electrical activity of Te atoms, a decrease in the electron mobility, and an increase in the contact resistance at atomic concentrations above 2 × 10{sup 20} cm{sup –3} are detected.

Complex Boron Redistribution in P+ Doped-polysilicon / Nitrogen Doped Silicon Bi-layers during Activation Annealing

Science.gov (United States)

Abadli, S.; Mansour, F.; Perrera, E. Bedel

We have investigated and modeled the complex phenomenon of boron (B) redistribution process in strongly doped silicon bilayers structure. A one-dimensional two stream transfer model well adapted to the particular structure of bi- layers and to the effects of strong-concentrations has been developed. This model takes into account the instantaneous kinetics of B transfer, trapping, clustering and segregation during the thermal B activation annealing. The used silicon bi-layers have been obtained by low pressure chemical vapor deposition (LPCVD) method, using in-situ nitrogen- doped-silicon (NiDoS) layer and strongly B doped polycrystalline-silicon (P+) layer. To avoid long redistributions, thermal annealing was carried out at relatively lowtemperatures (600 °C and 700 °C) for various times ranging between 30 minutes and 2 hours. The good adjustment of the simulated profiles with the experimental secondary ion mass spectroscopy (SIMS) profiles allowed a fundamental understanding about the instantaneous physical phenomena giving and disturbing the complex B redistribution profiles-shoulders kinetics.

Thermal oxidation effect on structural and optical properties of heavily doped phosphorus polycrystalline silicon films

Energy Technology Data Exchange (ETDEWEB)

Birouk, B.; Madi, D. [Universite de Jijel, Laboratoire d' Etudes et de Modelisation en Electrotechnique (LAMEL), Cite Ouled Aissa, BP 98, Jijel (Algeria)

2011-08-15

The study reported in this paper contributes to better understanding the thermal oxidation effect on structural and optical properties of polycrystalline silicon heavily in situ P-LPCVD films. The deposits, doped at levels 3 x 10{sup 19} and 1.6 x 10{sup 20} cm{sup -3}, have been elaborated from silane decomposition (400 mTorrs, 605 C) on monosilicon substrate oriented left angle 111 right angle. The thermal oxidation was performed at temperatures: 850 C during 1 hour, 1000, 1050, and 1100 C during 15 minutes. The XRD spectra analysis pointed out significant left angle 111 right angle texture evolution, while in the case of left angle 220 right angle and left angle 311 right angle textures, the intensities are practically invariant (variations fall in the uncertainty intervals). The optical characterizations showed that refractive index and absorption coefficient are very sensitive to the oxidation treatment, mainly when the doping level is not very high. We think that atomic oxygen acts as defects passivating agent leading to carriers' concentration increasing. Besides, the optical behavior is modeled in visible and near infrared, by a seven-term polynomial function n {sup 2}=f({lambda} {sup 2}), with alternate signs, instead of theoretically unlimited terms number from Drude's model. It has been shown that fitting parameters fall on Gaussian curves like they do in the theoretical model. (orig.)

Anodic oxidation of wastewater containing the Reactive Orange 16 Dye using heavily boron-doped diamond electrodes

International Nuclear Information System (INIS)

Migliorini, F.L.; Braga, N.A.; Alves, S.A.; Lanza, M.R.V.; Baldan, M.R.; Ferreira, N.G.

2011-01-01

Highlights: → Electrochemical advanced oxidation process was studied using BDD based anodes with different boron concentrations. → The difference between the non-active and active anodes for organics degradation. → The influence of morphologic and structural properties of BDD electrodes on the RO-16 dye degradation. - Abstract: Boron-doped diamond (BDD) films grown on the titanium substrate were used to study the electrochemical degradation of Reactive Orange (RO) 16 Dye. The films were produced by hot filament chemical vapor deposition (HFCVD) technique using two different boron concentrations. The growth parameters were controlled to obtain heavily doped diamond films. They were named as E1 and E2 electrodes, with acceptor concentrations of 4.0 and 8.0 x 10 21 atoms cm -3 , respectively. The boron levels were evaluated from Mott-Schottky plots also corroborated by Raman's spectra, which characterized the film quality as well as its physical property. Scanning Electron Microscopy showed well-defined microcrystalline grain morphologies with crystal orientation mixtures of (1 1 1) and (1 0 0). The electrode efficiencies were studied from the advanced oxidation process (AOP) to degrade electrochemically the Reactive Orange 16 azo-dye (RO16). The results were analyzed by UV/VIS spectroscopy, total organic carbon (TOC) and high-performance liquid chromatography (HPLC) techniques. From UV/VIS spectra the highest doped electrode (E2) showed the best efficiency for both, the aromaticity reduction and the azo group fracture. These tendencies were confirmed by the TOC and chromatographic measurements. Besides, the results showed a direct relationship among the BDD morphology, physical property, and its performance during the degradation process.

Direct identification of interstitial Mn in heavily p-type doped GaAs and evidence of its high thermal stability

CERN Document Server

Pereira, LMC; Correia, JG; Decoster, S; da Silva, MR; Araújo, JP; Vantomme, A

2011-01-01

We report on the lattice location of Mn in heavily p-type doped GaAs by means of $\\beta^{-}$-emission channeling from the decay of $^{56}$Mn. The majority of the Mn atoms substitute for Ga and up to 31% occupy the tetrahedral interstitial site with As nearest neighbors. Contrary to the general belief, we find that interstitial Mn is immobile up to 400$^{\\circ}$C, with an activation energy for diffusion of 1.7–2.3 eV. Such high thermal stability of interstitial Mn has significant implications on the strategies and prospects for achieving room temperature ferromagnetism in Ga$_{1−x}$Mn$_{x}$As.

High-current and low acceleration voltage arsenic ion implanted polysilicon-gate and source-drain electrode Si mos transistor

International Nuclear Information System (INIS)

Saito, Yasuyuki; Sugimura, Yoshiro; Sugihara, Michiyuki

1993-01-01

The fabrication process of high current arsenic (As) ion implanted polysilicon (Si) gate and source drain (SD) electrode Si n-channel metal oxide-semiconductor field effect transistor (MOSFET) was examined. Poly Si film n-type doping was performed by using high current (typical current: 2mA) and relatively low acceleration voltage (40keV) As ion implantation technique (Lintott series 3). It was observed that high dose As implanted poly Si films as is show refractoriness against radical fluorine excited by microwave. Using GCA MANN4800 (m/c ID No.2, resist: OFPR) mask pattern printing technique, the high current As ion implantation technique and radical fluorine gas phase etching (Chemical dry etching: CDE) technique, the n-channel Poly Si gate (ρs = ≅100Ω/□) enhancement MQSFETs(ρs source drain = ≅50Ω/□, SiO 2 gate=380 angstrom) with off-leak-less were obtained on 3 inch Czochralski grown 2Ωcm boron doped p type wafers (Osaka titanium). By the same process, a 8 bit single chip μ-processor with 26MHz full operation was performed

Design and Development of Polysilicon-based Microhotplate for Gas Sensing Application

Directory of Open Access Journals (Sweden)

Mahanth PRASAD

2009-04-01

Full Text Available The paper presents the design and development of a polysilicon-based microhotplate (MHP on a SiO2 membrane formed by bulk micromachining in orientation P-type silicon. The chip comprises four microheater cells, which can be used separately or in series combination. The chip size is 2.1 × 2.1 sq. mm. The design and simulation of a single-cell microhotplate is carried out using ANSYS. The complete fabrication process is described in this paper. The temperature coefficient of resistance (TCR of polysilicon resistors of values 5.7 kW and 3.36 kW has been measured as 0.69 × 10-3 and 0.5 × 10-3 per °C respectively. These values are used to estimate the temperature of the polysilicon heater by measuring the change in resistance value of the resistor on applying a voltage to it. Temperatures up to 367 °C have been calculated at low bias voltages. As the sensitivity of the gas sensing film is temperature dependent, the developed hotplate will be used as a platform for fabricating the gas sensors.

A study of different types of current mirrors using polysilicon TFTs

International Nuclear Information System (INIS)

Pappas, I; Nalpantidis, L; Kalenteridis, V; Siskos, S; Dimitriadis, C A; Hatzopoulos, A A

2005-01-01

Polysilicon thin-film technology has become of great interest due to the demand for large area electronic devices. Active matrix liquid crystal displays (AMLCDs) and active matrix organic light emitting displays (AMOLEDs) are among the fields where polysilicon thin-film transistors (poly-Si TFTs) are most commonly used. Such devices, generally, require analog signal processing. This fact makes the performance of basic analog blocks, such as current mirrors implemented with poly-Si TFTs, crucial. This paper examines the performance of various current mirror designs through simulation. Finally, a novel design of a current mirror is proposed aimed to be used in low voltage applications

Numerical analysis of a polysilicon-based resistive memory device

KAUST Repository

Berco, Dan; Chand, Umesh

2018-01-01

This study investigates a conductive bridge resistive memory device based on a Cu top electrode, 10-nm polysilicon resistive switching layer and a TiN bottom electrode, by numerical analysis for $$10^{3}$$103 programming and erase simulation cycles

Proceedings of the Flat-Plate Solar Array Project Workshop on Low-Cost Polysilicon for Terrestrial Photovoltaic Solar-Cell Applications

Science.gov (United States)

1986-01-01

Sessions conducted included: polysilicon material requirements; economics; process development in the U.S.; international process development; and polysilicon market and forecasts. Twenty-one papers were presented and discussed.

Control of polysilicon on-film particulates with on-product measurements

Science.gov (United States)

Barker, Judith B.; Chain, Elizabeth E.; Plachecki, Vincent E.

1997-08-01

Historically, a number of in-line particle measurements have been performed on separate test wafers included with product wafers during polysilicon processes. By performing film thickness and particulate measurements directly on product wafers, instead, a number of benefits accrue: (1) reduced test wafer usage, (2) reduced test wafer storage requirements, (3) reduced need for equipment to reclaim test wafers, (4) reduced need for direct labor to reclaim test wafers, and (5) reduced engineering 'false alarms' due to incorrectly processed test wafers. Implementation of on-product measurements for the polysilicon diffusion process required a number of changes in both philosophy and methodology. We show the necessary steps to implementation of on-product particle measurements with concern for overall manufacturing efficiency and the need to maintain appropriate control. Particle results from the Tencor 7600 Surfscan are presented.

Proceedings of the flat-plate solar array project workshop on low-cost polysilicon for terrestrial photovoltaic solar-cell applications

Energy Technology Data Exchange (ETDEWEB)

1986-02-01

Separate abstracts were prepared for 21 papers in this workshop proceedings. Topics covered include: polysilicon material requirements; economics; process developments in the USA and internationally; and the polysilicon market and forecasts. (LEW)

Toward deep blue nano hope diamonds: heavily boron-doped diamond nanoparticles.

Science.gov (United States)

Heyer, Steffen; Janssen, Wiebke; Turner, Stuart; Lu, Ying-Gang; Yeap, Weng Siang; Verbeeck, Jo; Haenen, Ken; Krueger, Anke

2014-06-24

The production of boron-doped diamond nanoparticles enables the application of this material for a broad range of fields, such as electrochemistry, thermal management, and fundamental superconductivity research. Here we present the production of highly boron-doped diamond nanoparticles using boron-doped CVD diamond films as a starting material. In a multistep milling process followed by purification and surface oxidation we obtained diamond nanoparticles of 10-60 nm with a boron content of approximately 2.3 × 10(21) cm(-3). Aberration-corrected HRTEM reveals the presence of defects within individual diamond grains, as well as a very thin nondiamond carbon layer at the particle surface. The boron K-edge electron energy-loss near-edge fine structure demonstrates that the B atoms are tetrahedrally embedded into the diamond lattice. The boron-doped diamond nanoparticles have been used to nucleate growth of a boron-doped diamond film by CVD that does not contain an insulating seeding layer.

A predictive model for the chemical vapor deposition of polysilicon in a cold wall, rapid thermal system

Energy Technology Data Exchange (ETDEWEB)

Toprac, A.J.; Trachtenberg, I.; Edgar, T.F. (Univ. of Texas, Austin, TX (United States). Dept. of Chemical Engineering)

1994-06-01

The chemical vapor deposition of polysilicon from thermally activated silane in a cold wall, single-wafer rapid thermal system was studied by experimentation at a variety of low pressure conditions, including very high temperatures. The effect of diluent gas on polysilicon deposition rates was examined using hydrogen, helium, and krypton. A mass-transfer model for the chemical vapor deposition of polysilicon in a cold wall, rapid thermal system was developed. This model was used to produce an empirical rate expression for silicon deposition from silane by regressing kinetic parameters to fit experimental data. The resulting model provided accurate predictions over widely varying conditions in the experimental data.

Boron deactivation in heavily boron-doped Czochralski silicon during rapid thermal anneal: Atomic level understanding

International Nuclear Information System (INIS)

Gao, Chao; Dong, Peng; Yi, Jun; Ma, Xiangyang; Yang, Deren; Lu, Yunhao

2014-01-01

The changes in hole concentration of heavily boron (B)-doped Czochralski silicon subjected to high temperature rapid thermal anneal (RTA) and following conventional furnace anneal (CFA) have been investigated. It is found that decrease in hole concentration, namely, B deactivation, is observed starting from 1050 °C and increases with RTA temperature. The following CFA at 300–500 °C leads to further B deactivation, while that at 600–800 °C results in B reactivation. It is supposed that the interaction between B atoms and silicon interstitials (I) thus forming BI pairs leads to the B deactivation during the high temperature RTA, and, moreover, the formation of extended B 2 I complexes results in further B deactivation in the following CFA at 300–500 °C. On the contrary, the dissociation of BI pairs during the following CFA at 600–800 °C enables the B reactivation. Importantly, the first-principles calculation results can soundly account for the above-mentioned supposition

Boron deactivation in heavily boron-doped Czochralski silicon during rapid thermal anneal: Atomic level understanding

Energy Technology Data Exchange (ETDEWEB)

Gao, Chao; Dong, Peng; Yi, Jun; Ma, Xiangyang, E-mail: luyh@zju.edu.cn, E-mail: mxyoung@zju.edu.cn; Yang, Deren [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Lu, Yunhao, E-mail: luyh@zju.edu.cn, E-mail: mxyoung@zju.edu.cn [International Center for New-Structured Materials and Laboratory of New-Structured Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

2014-01-20

The changes in hole concentration of heavily boron (B)-doped Czochralski silicon subjected to high temperature rapid thermal anneal (RTA) and following conventional furnace anneal (CFA) have been investigated. It is found that decrease in hole concentration, namely, B deactivation, is observed starting from 1050 °C and increases with RTA temperature. The following CFA at 300–500 °C leads to further B deactivation, while that at 600–800 °C results in B reactivation. It is supposed that the interaction between B atoms and silicon interstitials (I) thus forming BI pairs leads to the B deactivation during the high temperature RTA, and, moreover, the formation of extended B{sub 2}I complexes results in further B deactivation in the following CFA at 300–500 °C. On the contrary, the dissociation of BI pairs during the following CFA at 600–800 °C enables the B reactivation. Importantly, the first-principles calculation results can soundly account for the above-mentioned supposition.

Measurement of reaction heats using a polysilicon-based microcalorimetric sensor

NARCIS (Netherlands)

Vereshchagina, E.; Wolters, Robertus A.M.; Gardeniers, Johannes G.E.

2011-01-01

In this work we present a low-cost, low-power, small sample volume microcalorimetric sensor for the measurement of reaction heats. The polysilicon-based microcalorimetric sensor combines several advantages: (i) complementary metal oxide semiconductor technology (CMOS) for future integration; (ii)

Estimation of free carrier concentrations in high-quality heavily doped GaN:Si micro-rods by photoluminescence and Raman spectroscopy

Science.gov (United States)

Mohajerani, M. S.; Khachadorian, S.; Nenstiel, C.; Schimpke, T.; Avramescu, A.; Strassburg, M.; Hoffmann, A.; Waag, A.

2016-03-01

The controlled growth of highly n-doped GaN micro rods is one of the major challenges in the fabrication of recently developed three-dimensional (3D) core-shell light emitting diodes (LEDs). In such structures with a large active area, higher electrical conductivity is needed to achieve higher current density. In this contribution, we introduce high quality heavily-doped GaN:Si micro-rods which are key elements of the newly developed 3D core-shell LEDs. These structures were grown by metal-organic vapor phase epitaxy (MOVPE) using selective area growth (SAG). We employed spatially resolved micro-Raman and micro-photoluminescence (PL) in order to directly determine a free-carrier concentration profile in individual GaN micro-rods. By Raman spectroscopy, we analyze the low-frequency branch of the longitudinal optical (LO)-phonon-plasmon coupled modes and estimate free carrier concentrations from ≍ 2.4 × 1019 cm-3 up to ≍ 1.5 × 1020 cm-3. Furthermore, free carrier concentrations are determined by estimating Fermi energy level from the near band edge emission measured by low-temperature PL. The results from both methods reveal a good consistency.

Enhancement of Electrical Properties of Nanostructured Polysilicon Layers Through Hydrogen Passivation.

Science.gov (United States)

Zhou, D; Xu, T; Lambert, Y; Cristini-Robbe; Stiévenard, D

2015-12-01

The light absorption of polysilicon planar junctions can be improved using nanostructured top surfaces due to their enhanced light harvesting properties. Nevertheless, associated with the higher surface, the roughness caused by plasma etching and defects located at the grain boundary in polysilicon, the concentration of the recombination centers increases, leading to electrical performance deterioration. In this work, we demonstrate that wet oxidation combined with hydrogen passivation using SiN(x):H are the key technological processes to significantly decrease the surface recombination and improve the electrical properties of nanostructured n(+)-i-p junctions. Nanostructured surface is fabricated by nanosphere lithography in a low-cost and controllable approach. Furthermore, it has been demonstrated that the successive annealing of silicon nitride films has significant effect on the passivation quality, resulting in some improvements on the efficiency of the Si nanostructure-based solar cell device.

A manufacturing method for multi-layer polysilicon surface-micromachining technology

Energy Technology Data Exchange (ETDEWEB)

Sniegowski, J.J.; Rodgers, M.S.

1998-01-01

An advanced manufacturing technology which provides multi-layered polysilicon surface micromachining technology for advanced weapon systems is presented. Specifically, the addition of another design layer to a 4 levels process to create a 5 levels process allows consideration of fundamentally new architecture in designs for weapon advanced surety components.

Impact of doped boron concentration in emitter on high- and low-dose-rate damage in lateral PNP transistors

International Nuclear Information System (INIS)

Zheng Yuzhan; Lu Wu; Ren Diyuan; Wang Yiyuan; Wang Zhikuan; Yang Yonghui

2010-01-01

The characteristics of radiation damage under a high or low dose rate in lateral PNP transistors with a heavily or lightly doped emitter is investigated. Experimental results show that as the total dose increases, the base current of transistors would increase and the current gain decreases. Furthermore, more degradation has been found in lightly-doped PNP transistors, and an abnormal effect is observed in heavily doped transistors. The role of radiation defects, especially the double effects of oxide trapped charge, is discussed in heavily or lightly doped transistors. Finally, through comparison between the high- and low-dose-rate response of the collector current in heavily doped lateral PNP transistors, the abnormal effect can be attributed to the annealing of the oxide trapped charge. The response of the collector current, in heavily doped PNP transistors under high- and low-dose-rate irradiation is described in detail. (semiconductor integrated circuits)

High critical currents in heavily doped (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub x} superconductor tapes

Energy Technology Data Exchange (ETDEWEB)

Selvamanickam, V., E-mail: selva@uh.edu; Gharahcheshmeh, M. Heydari; Xu, A.; Galstyan, E.; Delgado, L. [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Rd., Houston, Texas 77204-4006 (United States); Cantoni, C. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37381 (United States)

2015-01-19

REBa{sub 2}Cu{sub 3}O{sub x} ((REBCO), RE = rare earth) superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50 K and fields of 2–30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (J{sub c}) above 20 MA/cm{sup 2} at 30 K, 3 T in heavily doped (25 mol. % Zr-added) (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub x} superconductor tapes, which is more than three times higher than the J{sub c} typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m{sup 3} have also been attained at 20 K. A composition map of lift factor in J{sub c} (ratio of J{sub c} at 30 K, 3 T to the J{sub c} at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO{sub 3} (BZO) nanocolumn defect density of nearly 7 × 10{sup 11 }cm{sup −2} as well as 2–3 nm sized particles rich in Cu and Zr have been found in the high J{sub c} films.

Low cost thin film poly-silicon solar cells

Energy Technology Data Exchange (ETDEWEB)

NONE

2005-07-01

This report presents the results of a project to design and develop a high density plasma based thin-film poly-silicon (TFPS) deposition system based on PQL proprietary advanced plasma technology to produce semiconductor quality TFPS for fabricating a TFPS solar cell. Details are given of the TFPS deposition system, the material development programme, solar cell structure, and cell efficiencies. The reproducibility of the deposition process and prospects for commercial exploitation are discussed.

Conductivity and superconductivity in heavily vacant diamond

Directory of Open Access Journals (Sweden)

S A Jafari

2009-08-01

Full Text Available   Motivated by the idea of impurity band superconductivity in heavily Boron doped diamond, we investigate the doping of various elements into diamond to address the question, which impurity band can offer a better DOS at the Fermi level. Surprisingly, we find that the vacancy does the best job in producing the largest DOS at the Fermi surface. To investigate the effect of disorder in Anderson localization of the resulting impurity band, we use a simple tight-binding model. Our preliminary study based on the kernel polynomial method shows that the impurity band is already localized at the concentration of 10-3. Around the vacancy concentration of 0.006 the whole spectrum of diamond becomes localized and quantum percolation takes place. Therefore to achieve conducting bands at concentrations on the scale of 5-10 percent, one needs to introduce correlations such as hopping among the vacancies .

The effect of fluorine in low thermal budget polysilicon emitters for SiGe heterojunction bipolar transistors

International Nuclear Information System (INIS)

Schiz, F.J.W.

1999-03-01

This thesis investigates the behaviour of fluorine in two types of polysilicon emitter. In the first type the emitter is deposited at 610 deg. C as polycrystalline silicon (p-Si). In the second type the emitter is deposited at 560 deg. C as amorphous silicon (α-Si). The amorphous silicon 1 then regrows to polysilicon during subsequent high temperature anneals. Remarkably different behaviour of fluorine is seen in as-deposited α-Si and as-deposited p-Si emitter bipolar transistors. In the most extreme case, fluorine-implanted as-deposited p-Si devices show a base current increase by a factor of 1.5 and equivalent α-Si devices a base current decrease by a factor of 10.0 compared to unimplanted devices. Cross-section TEM observations are made to study the structure of the polysilicon/silicon interface and SIMS measurements to study the distribution of the fluorine in the polysilicon. The TEM results correlate well with the electrical results and show that fluorine accelerates interfacial oxide breakup. Furthermore, they show that for a given thermal budget, more interfacial oxide breakup and thus more epitaxial regrowth is obtained for transistors with p-Si polysilicon emitters. This results in a lower emitter resistance, for example as low as 12Ωμm 2 for as-deposited p-Si devices. The base current suppression for as-deposited α-Si devices is explained by fluorine passivation of trapping states at the interface. Analysis of the fluorine SIMS profiles suggests that they do not resemble normal diffusion profiles, but are due to fluorine trapped at defects. It is shown that a reciprocal relationship exists between the fluorine dose in the bulk polysilicon layer and the fluorine dose at the interface. In as-deposited α-Si devices, there is more fluorine trapped at defects in the bulk polysilicon layer, so less is available to diffuse to the interface. As a result there is less interfacial oxide breakup and more passivation in the as-deposited α-Si devices. These

(Electro-) mechanical characteristics of electrostatically driven vacuum encapsulated polysilicon resonators

NARCIS (Netherlands)

Tilmans, H.A.C.; Tilmans, H.A.C.; Legtenberg, Rob; Legtenberg, R.; Schurer, H.; Schurer, H.; IJntema, D.J.; Ijntema, D.J.; Elwenspoek, Michael Curt; Fluitman, J.H.J.

The design, fabrication and performance of vacuum-encapsulated electrostatically driven polysilicon resonating beams, 210-510 μm long, 100 μm wide, and 1.5 μm thick, are described. The shortest beams have a fundamental frequency of 324 kHz, a gauge factor of 2400 and a quality factor of 600 at

Surface modification by vacuum annealing for field emission from heavily phosphorus-doped homoepitaxial (1 1 1) diamond

International Nuclear Information System (INIS)

Yamada, Takatoshi; Nebel, Christoph E.; Somu, Kumaragurubaran; Shikata, Shin-ichi

2008-01-01

The relationship between field emission properties and C 1s core level shifts of heavily phosphorus-doped homoepitaxial (1 1 1) diamond is investigated as a function of annealing temperature in order to optimize surface carbon bonding configurations for device applications. A low field emission threshold voltage is observed from surfaces annealed at 800 deg. C for hydrogen-plasma treated surface, while a low field emission threshold voltage of wet-chemical oxidized surface is observed after annealing at 900 deg. C. The C 1s core level by X-ray photoelectron spectroscopy (XPS) showed a shoulder peak at 1 eV below the main peak over 800 and 900 deg. C annealing temperature for hydrogen-plasma treated and wet-chemical oxidized surfaces, respectively. When the shoulder peak intensity is less than 10% of the main peak intensity, lower threshold voltages are observed. This is due to the carbon-reconstruction which gives rise to a small positive electron affinity. By increasing annealing temperature, the shoulder peak ratios also increase, which indicates that a surface graphitization takes place. This leads to higher threshold voltages

Electronic transport in heavily doped Ag/n-Si composite films

Directory of Open Access Journals (Sweden)

Clayton W. Bates Jr.

2013-10-01

Full Text Available Hall measurements characterized Ag/n-Si composite films 1 micron thick produced by magnetron co-sputtering onto high resistivity Si (111 substrates at 550°C. The targets were Ag and n-type Si doped with 3 × 1019/cm3 of antimony. Films were prepared with 13, 16 and 22 at. % Ag and measured over a temperature range 77–500°K. Conduction takes place at low temperatures by variable rang hopping in localized states at the Fermi level and by thermal activation over grain boundaries at higher temperatures. The Log Resistivity vs 1/kT curves for the three Ag concentrations vary in a similar manner, but decrease in magnitude with increasing Ag due to the smaller number of grain boundaries between Ag nanoparticles occurring with increasing Ag concentration. At low temperatures Hall mobilities are essentially independent of temperature as the carrier densities for the three Ag concentrations are constant from 77 to slightly under 300°K with resistivities varying by small amounts. The mobilities at all Ag concentrations increase with temperature and approach each other as the effects of grain boundaries become less important. This work presents for the first time the effects of metal particles embedded in a semiconductor on the transport properties of carriers in the semiconductor. Though these effects are for a given average particle size most of the results are expected to hold over a range of particle sizes. Free electrons produced in films containing 13 and 16 at. % Ag result in concentrations of 1.5 × 1019/cm3, one half the antimony doping, while those with 22 at. % Ag, the carrier concentrations are three orders of magnitude higher. These constant carrier concentrations are due to the metal-insulator transition that occurs in doped crystalline and polycrystalline silicon for carrier densities nc >3.9 × 1018/cm3. The three orders of magnitude higher carrier concentration produced in films with 22 at. % Ag is argued to be due to doping of the Si

Optimization of operating parameters in polysilicon chemical vapor deposition reactor with response surface methodology

Science.gov (United States)

An, Li-sha; Liu, Chun-jiao; Liu, Ying-wen

2018-05-01

In the polysilicon chemical vapor deposition reactor, the operating parameters are complex to affect the polysilicon's output. Therefore, it is very important to address the coupling problem of multiple parameters and solve the optimization in a computationally efficient manner. Here, we adopted Response Surface Methodology (RSM) to analyze the complex coupling effects of different operating parameters on silicon deposition rate (R) and further achieve effective optimization of the silicon CVD system. Based on finite numerical experiments, an accurate RSM regression model is obtained and applied to predict the R with different operating parameters, including temperature (T), pressure (P), inlet velocity (V), and inlet mole fraction of H2 (M). The analysis of variance is conducted to describe the rationality of regression model and examine the statistical significance of each factor. Consequently, the optimum combination of operating parameters for the silicon CVD reactor is: T = 1400 K, P = 3.82 atm, V = 3.41 m/s, M = 0.91. The validation tests and optimum solution show that the results are in good agreement with those from CFD model and the deviations of the predicted values are less than 4.19%. This work provides a theoretical guidance to operate the polysilicon CVD process.

Review of the workshop on low-cost polysilicon for terrestrial photovoltaic solar cell applications

Science.gov (United States)

Lutwack, R.

1986-01-01

Topics reviewed include: polysilicon material requirements; effects of impurities; requirements for high-efficiency solar cells; economics; development of silane processes; fluidized-bed processor development; silicon purification; and marketing.

Cathodoluminescence studies of anomalous ion implantation defect introduction in lightly and heavily doped liquid phase epitaxial GaAs:Sn

International Nuclear Information System (INIS)

Norris, C.B.; Barnes, C.E.

1980-01-01

The anomalous postrange defect introduction produced by shallow ion implantation in GaAs has been investigated in Sn-doped liquid phase epitaxial (LPE) material using depth-resolved cathodoluminescence in conjunction with layer removal by chemical etching. 100-keV Ne + or 200-keV Zn + ions were implanted into lightly or heavily Sn-doped LPE layers at temperatures between 80 and 300 K. All implantations were subsequently annealed at 300 K. Although the projected ion ranges for the implants were on the order of 1000 A, significant postrange damage was observed at far greater depths. At depths up to several microns, the damage introduction produced severe nonradiative recombination but simultaneously caused an apparent increase in the concentration of incumbent luminescence centers responsible for an extrinsic band near 1.39 eV. A weak damage-related band near 1.2 eV could also be seen in one instance. At depths of 5--30 μm, the postrange damage had the opposite effect of annihilating incumbent 1.39-eV luminescence centers. The efficiency of the damage introduction has a complicated temperature dependence which is significantly different for the ion/substrate combinations investigated. However, no conditions were found for which the damage introduction could be inhibited. While our measurements are the most extensive to date concerning the anomalous ion implant damage introduction in GaAs, the detailed mechanisms responsible for this effect still remain obscure owing in part to the limited understanding of defects in GaAs

Inhomogeneous electronic structures in heavily Pb-doped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} single crystals probed by low temperature STM/STS

Energy Technology Data Exchange (ETDEWEB)

Kinoda, Go; Nakao, Shoichiro; Motohashi, Teruki; Nakayama, Yuri; Shimizu, Keisuke; Shimoyama, Junichi; Kishio, Koji; Hanaguri, Tetsuo; Kitazawa, Koichi; Hasegawa, Tetsuya

2003-05-15

We have performed cryogenic scanning tunneling microscopy/spectroscopy (STM/STS) of heavily Pb-doped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} single crystals to investigate local electronic structures in the overdoped regime. The obtained STM/STS results at 4.3 K clearly showed local inhomogeneity of gap structure {delta} ({delta}=20-60 meV) in a scale of several nm, suggesting the coexistence of superconducting and pseudogap-like regions, even in the overdoped regime.

Effects of DC gate and drain bias stresses on the degradation of excimer laser crystallized polysilicon thin film transistors

International Nuclear Information System (INIS)

Kouvatsos, D N; Michalas, L; Voutsas, A T; Papaioannou, G J

2005-01-01

The effects of gate and drain bias stresses on thin film transistors fabricated in polysilicon films crystallized using the advanced sequential lateral solidification excimer laser annealing (SLS ELA) process, which yields very elongated polysilicon grains and allows the fabrication of TFTs without grain boundary barriers to current flow, are investigated as a function of the active layer thickness and of the TFT orientation relative to the grains. The application of hot carrier stress, with a condition of V GS = V DS /2, was determined to induce threshold voltage, subthreshold swing and transconductance degradation for TFTs in thicker polysilicon films and the associated stress-induced increase in the active layer trap density was evaluated. However, this device degradation was drastically reduced for TFTs fabricated in ultra-thin films. Furthermore, the application of the same stress condition to TFTs oriented vertically to the elongated grains resulted in similar threshold voltage shift but in substantially decreased subthreshold swing and transconductance degradation. The immunity of ultra-thin active layer devices to degradation under hot carrier stress clearly suggests the implementation of ultra thin SLS ELA polysilicon films for the fabrication of TFTs exhibiting not only high performance but, especially, the high reliability needed for integrated systems on panel

Wear mechanisms and friction parameters for sliding wear of micron-scale polysilicon sidewalls

NARCIS (Netherlands)

Alsem, D. H.; van der Hulst, R.; Stach, E. A.; Dugger, M. T.; De Hosson, J. Th. M.; Ritchie, R. O.

As tribological properties are critical factors in the reliability of silicon-based microelectromechanical systems, it is important to understand what governs wear and friction. Average dynamic friction, wear volumes and morphology have been studied for polysilicon devices fabricated using the

Rapid enhancement of nodal quasiparticle mass with heavily underdoping in Bi2212

Science.gov (United States)

Anzai, Hiroaki; Arita, Masashi; Namatame, Hirofumi; Taniguchi, Masaki; Ishikado, Motoyuki; Fujita, Kazuhiro; Ishida, Shigeyuki; Uchida, Shin-ichi; Ino, Akihiro

2018-05-01

We report substantial advance of our low-energy angle-resolved photoemission study of nodal quasiparticles in Bi2Sr2CaCu2O8+δ. The new data cover the samples from underdoped down to heavily underdoped levels. We also present the nodal Fermi velocities that determined by using an excitation-photon energy of hν = 7.0 eV over a wide doping range. The consistency between the results with hν = 8.1 and 7.0 eV allows us to rule out the effect of photoemission matrix elements. In comparison with the data previously reported, the nodal effective mass increases by a factor of ∼ 1.5 in going from optimally doped to heavily underdoped levels. We find a rapid enhancement of the nodal quasiparticle mass at low doping levels near the superconductor-to-insulator transition. The effective coupling spectrum, λ (ω) , is extracted directly from the energy derivatives of the quasiparticle dispersion and scattering rate, as a causal function of the mass enhancement factor. A steplike increase in Reλ (ω) around ∼ 65 meV is demonstrated clearly by the Kramers-Kronig transform of Imλ (ω) . To extract the low-energy renormalization effect, we calculated a simple model for the electron-boson interaction. This model reveals that the contribution of the renormalization at | ω | ≤ 15 meV to the quasiparticle mass is larger than that around 65 meV in underdoped samples.

Surface photovoltage in heavily doped GaN:Si,Zn

Science.gov (United States)

McNamara, J. D.; Behrends, A.; Mohajerani, M. S.; Bakin, A.; Waag, A.; Baski, A. A.; Reshchikov, M. A.

2014-02-01

In n-type GaN, an upward band bending of about 1 eV is caused by negative charge at the surface. UV light reduces the band bending by creating a surface photovoltage (SPV), which can be measured by a Kelvin probe. Previously, we reported a fast SPV signal of about 0.6 eV in undoped and moderately doped GaN. In this work, we have studied degenerate GaN co-doped with Zn and Si, with a Si concentration of about 1019 cm-3 and a Zn concentration of 6×1017 cm-3. At room temperature, a fast component of about 0.6 eV was observed. However, after preheating the sample at 600 K for one hour and subsequently cooling the sample to 300 K (all steps performed in vacuum), the fast component disappeared. Instead, a very slow (minutes) and logarithmic in time rise of the SPV was observed with UV illumination. The total change in SPV was about 0.4 eV. This slow SPV transient can be reversibly converted into the "normal" fast (subsecond) rise by letting air or dry oxygen in at room temperature. Possible explanations of the observed unusual SPV transients are discussed.

A fully integrated, monolithic, cryogenic charge sensitive preamplifier using N-channel JFETs and polysilicon resistors

International Nuclear Information System (INIS)

Jung, T.S.; Guckel, H.; Seefeldt, J.; Ott, G.; Ahn, Y.C.

1994-01-01

In this paper, an integrated charge preamplifier to be used with small (10--30 mm 2 ) Si(Li) and Ge(Li) X-ray detectors is described. The preamplifier is designed to operate at cryogenic temperatures (∼100 K to 160 K) for the best performance. An N-channel JFET process technology for integrated charge sensitive preamplifiers has been developed. The process integrates multiple pinch-off voltage JFETs fabricated in an n-type epitaxial layer on a low resistivity p-type substrate. The process also incorporates polysilicon resistors integrated on the same die as the JFETs. The optimized polysilicon resistors exhibit 1/f noise nearly as good as metal film resistors at the same current. Results for integrated amplifier are discussed

Metal-insulator transition and superconductivity in heavily boron-doped diamond and related materials

Energy Technology Data Exchange (ETDEWEB)

Achatz, Philipp

2009-05-15

During this PhD project, the metal-insulator transition and superconductivity of highly boron-doped single crystal diamond and related materials have been investigated. The critical boron concentration n{sub c} for the metal-insulator transition was found to be the same as for the normal-superconductor transition. All metallic samples have been found to be superconducting and we were able to link the occurence of superconductivity to the proximity to the metal-insulator transition. For this purpose, a scaling law approach based on low temperature transport was proposed. Furthermore, we tried to study the nature of the superconductivity in highly boron doped single crystal diamond. Raman spectroscopy measurements on the isotopically substituted series suggest that the feature occuring at low wavenumbers ({approx} 500 cm{sup -1}) is the A1g vibrational mode associated with boron dimers. Usual Hall effect measurements yielded a puzzling situation in metallic boron-doped diamond samples, leading to carrier concentrations up to a factor 10 higher than the boron concentration determined by secondary ion mass spectroscopy (SIMS). The low temperature transport follows the one expected for a granular metal or insulator, depending on the interplay of intergranular and intragranular (tunneling) conductance. The metal-insulator transition takes place at a critical conductance g{sub c}. The granularity also influences significantly the superconducting properties by introducing the superconducting gap {delta} in the grain and Josephson coupling J between superconducting grains. A peak in magnetoresistance is observed which can be explained by superconducting fluctuations and the granularity of the system. Additionally we studied the low temperature transport of boron-doped Si samples grown by gas immersion laser doping, some of which yielded a superconducting transition at very low temperatures. Furthermore, preliminary results on the LO-phonon-plasmon coupling are shown for the

Metal-insulator transition and superconductivity in heavily boron-doped diamond and related materials

International Nuclear Information System (INIS)

Achatz, Philipp

2009-01-01

During this PhD project, the metal-insulator transition and superconductivity of highly boron-doped single crystal diamond and related materials have been investigated. The critical boron concentration n c for the metal-insulator transition was found to be the same as for the normal-superconductor transition. All metallic samples have been found to be superconducting and we were able to link the occurence of superconductivity to the proximity to the metal-insulator transition. For this purpose, a scaling law approach based on low temperature transport was proposed. Furthermore, we tried to study the nature of the superconductivity in highly boron doped single crystal diamond. Raman spectroscopy measurements on the isotopically substituted series suggest that the feature occuring at low wavenumbers (∼ 500 cm -1 ) is the A1g vibrational mode associated with boron dimers. Usual Hall effect measurements yielded a puzzling situation in metallic boron-doped diamond samples, leading to carrier concentrations up to a factor 10 higher than the boron concentration determined by secondary ion mass spectroscopy (SIMS). The low temperature transport follows the one expected for a granular metal or insulator, depending on the interplay of intergranular and intragranular (tunneling) conductance. The metal-insulator transition takes place at a critical conductance g c . The granularity also influences significantly the superconducting properties by introducing the superconducting gap Δ in the grain and Josephson coupling J between superconducting grains. A peak in magnetoresistance is observed which can be explained by superconducting fluctuations and the granularity of the system. Additionally we studied the low temperature transport of boron-doped Si samples grown by gas immersion laser doping, some of which yielded a superconducting transition at very low temperatures. Furthermore, preliminary results on the LO-phonon-plasmon coupling are shown for the first time in aluminum-doped

Continuous growth of low-temperature Si epitaxial layer with heavy phosphorous and boron doping using photoepitaxy

International Nuclear Information System (INIS)

Yamazaki, T.; Minakata, H.; Ito, T.

1990-01-01

The authors grew p + -n + silicon epitaxial layers, heavily doped with phosphorus and boron, continuously at 650 degrees C using low-temperature photoepitaxy. Then N + photoepitaxial layer with a phosphorus concentration above 10 17 cm -3 grown on p - substrate shows high-density surface pits, and as a result, poor crystal quality. However, when this n + photoepitaxial layer is grown continuously on a heavily boron-doped p + photoepitaxial layer, these surface pits are drastically decreased, disappearing completely above a hole concentration of 10 19 cm -3 in the p + photoepitaxial layer. The phosphorus activation ratio and electron Hall mobility in the heavily phosphorus-doped n + photoexpitaxial layer were also greatly improved. The authors investigated the cause of the surface pitting using a scanning transmission electron microscope, secondary ion mass spectroscopy, and energy-dispersive x-ray spectroscopy. They characterized the precipitation of phosphorus atoms on the crystal surface at the initial stage of the heavily phosphorus-doped n + photoexpitaxial layer growth

Integrated investigation approach for determining mechanical properties of poly-silicon membranes

OpenAIRE

Brueckner, J.; Dehe, A.; Auerswald, E.; Dudek, R.; Michel, B.; Rzepka, S.

2014-01-01

A methodology is presented for determining mechanical properties of free-standing thin films such as poly-silicon membranes. The integrated investigation approach comprises test structure development, mechanical testing, and numerical simulation. All membrane test structures developed and manufactured consist of the same material but have different stiffness due to variations in the geometric design. The mechanical tests apply microscopic loads utilizing a nanoindentation tool. Young's modulu...

Electron transport in heavily doped GdN

Science.gov (United States)

Maity, T.; Trodahl, H. J.; Natali, F.; Ruck, B. J.; Vézian, S.

2018-01-01

We report measurements of electron transport phenomena in the intrinsic ferromagnetic semiconductor GdN doped with 1.3 ×1021cm-3 electrons. The conductivity, carrier concentration, and thermoelectric power are compared with expectations based on an LSDA+U band structure. In the ferromagnetic state the carriers fill the majority-spin conduction band pockets to the bottom of the minority-spin band. The resistance implies an electron mobility of 18 cm2V-1s-1 at zero temperature, and in turn a mean-free path of 10-30 nm. Spin disorder scattering rapidly reduces the mobility near the 70 K Curie temperature (TC). The thermoelectric power is negative in the paramagnetic phase, as expected for a n -type conductor, with a magnitude that is in agreement with the Fermi energy implied by the band structure. The thermopower reverses sign to be positive in the ferromagnetic phase, which correlates with a strongly temperature-dependent electron diffusion from spin-disorder scattering that increases rapidly as the temperature rises toward TC.

Contribution to the study, by magnetic resonance, of the properties of heavily doped silicon at low temperature

International Nuclear Information System (INIS)

Jerome, D.

1965-10-01

The magnetic properties of heavily doped silicon at low temperature have been studied in a range of concentration on either side of the Mott transition. For impurity densities less than that of the transition a magnetic double resonance method allows the exchange coupling between localized donors to be measured, and in addition the existence of paramagnetic centers (pairs of neutral and ionized donors) is demonstrated. The behaviour of the spin-lattice relaxation of 29 Ci is explained in terms of the dipolar coupling between nuclei and paramagnetic centers. In the range of concentration 10 16 -10 17 impurities/cm 3 , the concentration dependent relaxation of donors is studied experimentally. A theoretical explanation is proposed for the latter mechanism, the basis of which is the presence of ionized pairs of donors. At increasing impurity concentrations the electronic delocalization increases. For the concentration of 2.5 X 10 18 P/cm 3 the hyperfine coupling is responsible for the 29 Si relaxation. It is shown that the electron density has a very large maximum near the impurities in the metallic domain of concentrations. An estimation of the impurity band width (19 deg. K) is deduced from the measurement of the paramagnetic part of the electronic susceptibility at low temperature. (author) [fr

Thermal equilibrium concentration of intrinsic point defects in heavily doped silicon crystals - Theoretical study of formation energy and formation entropy in area of influence of dopant atoms-

Science.gov (United States)

Kobayashi, K.; Yamaoka, S.; Sueoka, K.; Vanhellemont, J.

2017-09-01

It is well known that p-type, neutral and n-type dopants affect the intrinsic point defect (vacancy V and self-interstitial I) behavior in single crystal Si. By the interaction with V and/or I, (1) growing Si crystals become more V- or I-rich, (2) oxygen precipitation is enhanced or retarded, and (3) dopant diffusion is enhanced or retarded, depending on the type and concentration of dopant atoms. Since these interactions affect a wide range of Si properties ranging from as-grown crystal quality to LSI performance, numerical simulations are used to predict and to control the behavior of both dopant atoms and intrinsic point defects. In most cases, the thermal equilibrium concentrations of dopant-point defect pairs are evaluated using the mass action law by taking only the binding energy of closest pair to each other into account. The impacts of dopant atoms on the formation of V and I more distant than 1st neighbor and on the change of formation entropy are usually neglected. In this study, we have evaluated the thermal equilibrium concentrations of intrinsic point defects in heavily doped Si crystals. Density functional theory (DFT) calculations were performed to obtain the formation energy (Ef) of the uncharged V and I at all sites in a 64-atom supercell around a substitutional p-type (B, Ga, In, and Tl), neutral (C, Ge, and Sn) and n-type (P, As, and Sb) dopant atom. The formation (vibration) entropies (Sf) of free I, V and I, V at 1st neighboring site from B, C, Sn, P and As atoms were also calculated with the linear response method. The dependences of the thermal equilibrium concentrations of trapped and total intrinsic point defects (sum of free I or V and I or V trapped with dopant atoms) on the concentrations of B, C, Sn, P and As in Si were obtained. Furthermore, the present evaluations well explain the experimental results of the so-called ;Voronkov criterion; in B and C doped Si, and also the observed dopant dependent void sizes in P and As doped Si

Modeling of gas-phase chemistry in the chemical vapor deposition of polysilicon in a cold wall system

Energy Technology Data Exchange (ETDEWEB)

Toprac, A.J.; Edgar, T.F.; Trachtenberg, I. (Univ. of Texas, Austin, TX (United States). Dept. of Chemical Engineering)

1993-06-01

The relative contribution of gas-phase chemistry to deposition processes is an important issue both from the standpoint of operation and modeling of these processes. In polysilicon deposition from thermally activated silane in a cold wall rapid thermal chemical vapor deposition (RTCVD) system, the relative contribution of gas-phase chemistry to the overall deposition rate was examined by a mass-balance model. Evaluating the process at conditions examined experimentally, the model indicated that gas-phase reactions may be neglected to good accuracy in predicting polysilicon deposition rate. The model also provided estimates of the level of gas-phase generated SiH[sub 2] associated with deposition on the cold-process chamber walls.

Polysilicon high frequency devices for large area electronics: Characterization, simulation and modeling

Energy Technology Data Exchange (ETDEWEB)

Botrel, J L [CEA-LETI 17, rue des Martyrs 38054 Grenoble (France); IMEP 23, rue des Martyrs 38016 Grenoble (France)], E-mail: jean-loius.botrel@cea.fr; Savry, O; Rozeau, O; Templier, F [CEA-LETI 17, rue des Martyrs 38054 Grenoble (France); Jomaah, J [IMEP 23, rue des Martyrs 38016 Grenoble (France)

2007-07-16

Laser Crystallised Polysilicon Thin Film Transistors have now sufficient good conduction properties to be used in high-frequency applications. In this work, we report the results for 5 {mu}m long polysilicon TFTs obtained at frequencies up to several hundred MHz for applications such as RFID tags or System-On-Panel. In order to investigate the device operation, DC and AC two-dimensional simulations of these devices in the Effective Medium framework have been performed. In the light of simulation results, the effects of carrier trapping and carrier transit on the device capacitances as a function of dimensions are analysed and compared. An equivalent small-signal circuit which accounts for the behaviour of these transistors in all regions of operation is proposed and a model for the most relevant elements of this circuit is presented. To validate our simulation results, scattering-parameters (S-parameters) measurements are performed for several structures such as multi-finger, serpentine and linear architectures and the most meaningful parameters will be given. Cut-off frequencies as high as 300 MHz and maximum oscillation frequencies of about 600 MHz have been extracted.

Heavy doping effects in high efficiency silicon solar cells

Science.gov (United States)

Lindholm, F. A.; Neugroschel, A.

1986-01-01

The temperature dependence of the emitter saturation current for bipolar devices was studied by varying the surface recombination velocity at the emitter surface. From this dependence, the value was derived for bandgap narrowing that is in better agreement with other determinations that were obtained from the temperature dependence measure on devices with ohmic contacts. Results of the first direct measurement of the minority-carrier transit time in a transparent heavily doped emitter layer were reported. The value was obtained by a high-frequency conductance method recently developed and used for doped Si. Experimental evidence is presented for significantly greater charge storage in highly excited silicon near room temperature than conventional theory would predict. These data are compared with various data for delta E sub G in heavily doped silicon.

Tuning electronic properties of In2O3 nanowires by doping control

International Nuclear Information System (INIS)

Lei, B.; Li, C.; Zhang, D.; Tang, D.; Zhou, C.

2004-01-01

We present two effective routes to tune the electronic properties of single-crystalline In 2 O 3 nanowires by controlling the doping. The first method involves using different O 2 concentrations during the synthesis. Lightly (heavily) doped nanowires were produced by using high (low) O 2 concentrations, respectively, as revealed by the conductances and threshold voltages of nanowire-based field-effect transistors. Our second method exploits post-synthesis baking, as baking heavily doped nanowires in ambient air led to suppressed conduction and a positive shift of the threshold voltage, whereas baking lightly doped nanowires in vacuum displayed the opposite behavior. Our approaches offer viable ways to tune the electronic properties of many nonstoichiometric metal oxide systems such as In 2 O 3 , SnO 2 , and ZnO nanowires for various applications

Spectroscopic XPEEM of highly conductive SI-doped GaN wires

Energy Technology Data Exchange (ETDEWEB)

Renault, O., E-mail: olivier.renault@cea.fr [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Morin, J. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Tchoulfian, P. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); CNRS, Inst. NEEL, F-38042 Grenoble (France); Chevalier, N. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Feyer, V. [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, D-52425 Jülich (Germany); Pernot, J. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CNRS, Inst. NEEL, F-38042 Grenoble (France); Institut Universitaire de France, F-75005 Paris (France); Schneider, C.M. [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, D-52425 Jülich (Germany)

2015-12-15

Using soft X-ray photoelectron emission microscopy (XPEEM), complemented by scanning Auger microscopy (SAM) and scanning capacitance microscopy, we have quantitatively studied the incorporation of silicon and band bending at the surface (m-facet) of an individual, highly conductive Si-doped GaN micro-wires (Tchoulfian et al., Applied Physics Letters 102 (12), 2013). Electrically active n-dopants Si atoms in Ga interstitial sites are detected as nitride bonding states in the high-resolution Si2p core level spectra, and represent only a small fraction (<10%) of the overall Si surface concentration measured by SAM. The derived carrier concentration of 2×10{sup 21} at cm{sup −3} is in reasonable agreement with electrical measurements. A consistent surface band bending of ~1 eV is directly evidenced by surface photo-voltage measurements. Such an approach combining different surface-sensitive microscopies is of interest for studying other heavily doped semiconducting wires. - Highlights: • XPEEM analysis of state-of-the-art, heavily doped GaN wires with insights on the issue of the origin of the increased conductivity. • Combined microscopic approach with Scanning Auger microscopy and X-ray Photoeletron Emission Microscopy, to quantity the electrically active Si-dopants in GaN. • The determined concentration is found in reasonable agreement with the one derived from bulk electrical measurements. • The proposed method is of interest for studying the electronics and chemistry of doping in other heavily doped semiconducting wires.

Faraday rotation and photoluminescence in heavily Tb(3+)-doped GeO2-B2O3-Al2O3-Ga2O3 glasses for fiber-integrated magneto-optics.

Science.gov (United States)

Gao, Guojun; Winterstein-Beckmann, Anja; Surzhenko, Oleksii; Dubs, Carsten; Dellith, Jan; Schmidt, Markus A; Wondraczek, Lothar

2015-03-10

We report on the magneto-optical (MO) properties of heavily Tb(3+)-doped GeO2-B2O3-Al2O3-Ga2O3 glasses towards fiber-integrated paramagnetic MO devices. For a Tb(3+) ion concentration of up to 9.7 × 10(21) cm(-3), the reported glass exhibits an absolute negative Faraday rotation of ~120 rad/T/m at 632.8 nm. The optimum spectral ratio between Verdet constant and light transmittance over the spectral window of 400-1500 nm is found for a Tb(3+) concentration of ~6.5 × 10(21) cm(-3). For this glass, the crystallization stability, expressed as the difference between glass transition temperature and onset temperature of melt crystallization exceeds 100 K, which is a prerequisite for fiber drawing. In addition, a high activation energy of crystallization is achieved at this composition. Optical absorption occurs in the NUV and blue spectral region, accompanied by Tb(3+) photoluminescence. In the heavily doped materials, a UV/blue-to-green photo-conversion gain of ~43% is achieved. The lifetime of photoluminescence is ~2.2 ms at a stimulated emission cross-section σem of ~1.1 × 10(-21) cm(2) for ~ 5.0 × 10(21) cm(-3) Tb(3+). This results in an optical gain parameter σem*τ of ~2.5 × 10(-24) cm(2)s, what could be of interest for implementation of a Tb(3+) fiber laser.

Faraday rotation and photoluminescence in heavily Tb3+-doped GeO2-B2O3-Al2O3-Ga2O3 glasses for fiber-integrated magneto-optics

Science.gov (United States)

Gao, Guojun; Winterstein-Beckmann, Anja; Surzhenko, Oleksii; Dubs, Carsten; Dellith, Jan; Schmidt, Markus A.; Wondraczek, Lothar

2015-01-01

We report on the magneto-optical (MO) properties of heavily Tb3+-doped GeO2-B2O3-Al2O3-Ga2O3 glasses towards fiber-integrated paramagnetic MO devices. For a Tb3+ ion concentration of up to 9.7 × 1021 cm−3, the reported glass exhibits an absolute negative Faraday rotation of ~120 rad/T/m at 632.8 nm. The optimum spectral ratio between Verdet constant and light transmittance over the spectral window of 400–1500 nm is found for a Tb3+ concentration of ~6.5 × 1021 cm−3. For this glass, the crystallization stability, expressed as the difference between glass transition temperature and onset temperature of melt crystallization exceeds 100 K, which is a prerequisite for fiber drawing. In addition, a high activation energy of crystallization is achieved at this composition. Optical absorption occurs in the NUV and blue spectral region, accompanied by Tb3+ photoluminescence. In the heavily doped materials, a UV/blue-to-green photo-conversion gain of ~43% is achieved. The lifetime of photoluminescence is ~2.2 ms at a stimulated emission cross-section σem of ~1.1 × 10−21 cm2 for ~ 5.0 × 1021 cm−3 Tb3+. This results in an optical gain parameter σem*τ of ~2.5 × 10−24 cm2s, what could be of interest for implementation of a Tb3+ fiber laser. PMID:25754819

Demonstration of pattern transfer into sub-100 nm polysilicon line/space features patterned with extreme ultraviolet lithography

International Nuclear Information System (INIS)

Cardinale, G. F.; Henderson, C. C.; Goldsmith, J. E. M.; Mangat, P. J. S.; Cobb, J.; Hector, S. D.

1999-01-01

In two separate experiments, we have successfully demonstrated the transfer of dense- and loose-pitch line/space (L/S) photoresist features, patterned with extreme ultraviolet (EUV) lithography, into an underlying hard mask material. In both experiments, a deep-UV photoresist (∼90 nm thick) was spin cast in bilayer format onto a hard mask (50-90 nm thick) and was subsequently exposed to EUV radiation using a 10x reduction EUV exposure system. The EUV reticle was fabricated at Motorola (Tempe, AZ) using a subtractive process with Ta-based absorbers on Mo/Si multilayer mask blanks. In the first set of experiments, following the EUV exposures, the L/S patterns were transferred first into a SiO 2 hard mask (60 nm thick) using a reactive ion etch (RIE), and then into polysilicon (350 nm thick) using a triode-coupled plasma RIE etcher at the University of California, Berkeley, microfabrication facilities. The latter etch process, which produced steep (>85 degree sign ) sidewalls, employed a HBr/Cl chemistry with a large (>10:1) etch selectivity of polysilicon to silicon dioxide. In the second set of experiments, hard mask films of SiON (50 nm thick) and SiO 2 (87 nm thick) were used. A RIE was performed at Motorola using a halogen gas chemistry that resulted in a hard mask-to-photoresist etch selectivity >3:1 and sidewall profile angles ≥85 degree sign . Line edge roughness (LER) and linewidth critical dimension (CD) measurements were performed using Sandia's GORA(c) CD digital image analysis software. Low LER values (6-9 nm, 3σ, one side) and good CD linearity (better than 10%) were demonstrated for the final pattern-transferred dense polysilicon L/S features from 80 to 175 nm. In addition, pattern transfer (into polysilicon) of loose-pitch (1:2) L/S features with CDs≥60 nm was demonstrated. (c) 1999 American Vacuum Society

Investigation of a new low cost and low consumption single poly-silicon memory

Directory of Open Access Journals (Sweden)

Patrick Calenzo

2010-10-01

Full Text Available In this paper is presented an investigation on a new low cost and voltage consumption single poly-silicon memory cell for passive RFID (Radio Frequency IDentificationapplications. This structure is low cost due to its single poly-silicon design. This memory cell has two particularities : the first one is that no deported capacitor is necessary to program this cell which allows to reduce the structure size to 1.1μm². The second one is the way the cell is erased. A Zener diode is used to generate carriers in order to be injected into the floating gate. This Zener diode is one of the key points for the functionality that has to be validated with some electrical trials. These trials permit to integrate and use the Zener diodes measured in simulations of the complete memory cell. This is done to validate the best candidate between the Zener diodes used for the cell and highlight the efficiency in consumption and rapidity to erase the cell. Besides, the writing and the reading cases are simulated in order to show the low consumption required by the cell during these phases.

Near-thermal limit gating in heavily doped III-V semiconductor nanowires using polymer electrolytes

Science.gov (United States)

Ullah, A. R.; Carrad, D. J.; Krogstrup, P.; Nygârd, J.; Micolich, A. P.

2018-02-01

Doping is a common route to reducing nanowire transistor on-resistance but it has limits. A high doping level gives significant loss in gate performance and ultimately complete gate failure. We show that electrolyte gating remains effective even when the Be doping in our GaAs nanowires is so high that traditional metal-oxide gates fail. In this regime we obtain a combination of subthreshold swing and contact resistance that surpasses the best existing p -type nanowire metal-oxide semiconductor field-effect transistors (MOSFETs). Our subthreshold swing of 75 mV/dec is within 25 % of the room-temperature thermal limit and comparable with n -InP and n -GaAs nanowire MOSFETs. Our results open a new path to extending the performance and application of nanowire transistors, and motivate further work on improved solid electrolytes for nanoscale device applications.

Gettering effects in RAD polysilicon ribbons: An XPS/AES study

Energy Technology Data Exchange (ETDEWEB)

Amarray, E.; Deville, J.P.; Quesada, J.

1987-03-01

Evidence for gettering effects during the various heat treatments applied to RAD ribbons were investigated with surface analysis methods. These heat treatments occur either during the burning-off process of the carbon support or during the POCl/sub 3/ diffusion, and transport metallic impurities near the surface of the sample. Oxidation of clean silicon surfaces, cleaved either in air or ultra-high vacuum, has shown that the same metallic impurities are brought near the surface by this treatment alone. It is thus suggested that controlled oxidations and heat treatments can be used to improve the electrical properties of polysilicon, and especially of ribbons.

Surface plasmon enhanced SWIR absorption at the ultra n-doped substrate/PbSe nanostructure layer interface

Science.gov (United States)

Wittenberg, Vladimir; Rosenblit, Michael; Sarusi, Gabby

2017-08-01

This work presents simulation results of the plasmon enhanced absorption that can be achieved in the short wavelength infrared (SWIR - 1200 nm to 1800 nm) spectral range at the interface between ultra-heavily doped substrates and a PbSe nanostructure non-epitaxial growth absorbing layer. The absorption enhancement simulated in this study is due to surface plasmon polariton (SPP) excitation at the interface between these ultra-heavily n-doped GaAs or GaN substrates, which are nearly semimetals to SWIR light, and an absorption layer made of PbSe nano-spheres or nano-columns. The ultra-heavily doped GaAs or GaN substrates are simulated as examples, based on the Drude-Lorentz permittivity model. In the simulation, the substrates and the absorption layer were patterned jointly to forma blazed lattice, and then were back-illuminated using SWIR with a central wavelength of 1500 nm. The maximal field enhancement achieved was 17.4 with a penetration depth of 40 nm. Thus, such architecture of an ultra-heavily doped semiconductor and infrared absorbing layer can further increase the absorption due to the plasmonic enhanced absorption effect in the SWIR spectral band without the need to use a metallic layer as in the case of visible light.

Poly-silicon quantum-dot single-electron transistors

International Nuclear Information System (INIS)

Kang, Kwon-Chil; Lee, Joung-Eob; Lee, Jung-Han; Lee, Jong-Ho; Shin, Hyung-Cheol; Park, Byung-Gook

2012-01-01

For operation of a single-electron transistors (SETs) at room temperature, we proposed a fabrication method for a SET with a self-aligned quantum dot by using polycrystalline silicon (poly-Si). The self-aligned quantum dot is formed by the selective etching of a silicon nanowire on a planarized surface and the subsequent deposition and etch-back of poly-silicon or chemical mechanical polishing (CMP). The two tunneling barriers of the SET are fabricated by thermal oxidation. Also, to decrease the leakage current and control the gate capacitance, we deposit a hard oxide mask layer. The control gate is formed by using an electron beam and photolithography on chemical vapor deposition (CVD). Owing to the small capacitance of the narrow control gate due to the tetraethyl orthosilicate (TEOS) hard mask, we observe clear Coulomb oscillation peaks and differential trans-conductance curves at room temperature. The clear oscillation period of the fabricated SET is 2.0 V.

Development of AC-coupled, poly-silicon biased, p-on-n silicon strip detectors in India for HEP experiments

Science.gov (United States)

Jain, Geetika; Dalal, Ranjeet; Bhardwaj, Ashutosh; Ranjan, Kirti; Dierlamm, Alexander; Hartmann, Frank; Eber, Robert; Demarteau, Marcel

2018-02-01

P-on-n silicon strip sensors having multiple guard-ring structures have been developed for High Energy Physics applications. The study constitutes the optimization of the sensor design, and fabrication of AC-coupled, poly-silicon biased sensors of strip width of 30 μm and strip pitch of 55 μm. The silicon wafers used for the fabrication are of 4 inch n-type, having an average resistivity of 2-5 k Ω cm, with a thickness of 300 μm. The electrical characterization of these detectors comprises of: (a) global measurements of total leakage current, and backplane capacitance; (b) strip and voltage scans of strip leakage current, poly-silicon resistance, interstrip capacitance, interstrip resistance, coupling capacitance, and dielectric current; and (c) charge collection measurements using ALiBaVa setup. The results of the same are reported here.

Efficiency enhancement of InGaN/GaN light-emitting diodes with pin-doped GaN quantum barrier

International Nuclear Information System (INIS)

Sirkeli, Vadim P; Al-Daffaie, Shihab; Oprea, Ion; Küppers, Franko; Hartnagel, Hans L; Yilmazoglu, Oktay; Ong, Duu Sheng

2017-01-01

Blue InGaN/GaN light-emitting diodes with undoped, heavily Si-doped, Si delta-doped, heavily Mg-doped, Mg delta-doped, and Mg–Si pin-doped GaN barrier are investigated numerically. The simulation results demonstrate that the Mg–Si pin-doping in the GaN barrier effectively reduces the polarization-induced electric field between the InGaN well and the GaN barrier in the multiple quantum well, suppresses the quantum-confined Stark effect, and enhances the hole injection and electron confinement in the active region. For this light-emitting diode (LED) device structure, we found that the turn-on voltage is 2.8 V, peak light emission is at 415.3 nm, and internal quantum efficiency is 85.9% at 100 A cm −2 . It is established that the LED device with Mg–Si pin-doping in the GaN barrier has significantly improved efficiency and optical output power performance, and lower efficiency droop up to 400 A cm −2 compared with LED device structures with undoped or Si(Mg)-doped GaN barrier. (paper)

Development of the silane process for the production of low-cost polysilicon

Science.gov (United States)

Iya, S. K.

1986-01-01

It was recognized that the traditional hot rod type deposition process for decomposing silane is energy intensive, and a different approach for converting silane to silicon was chosen. A 1200 metric tons/year capacity commercial plant was constructed in Moses Lake, Washington. A fluidized bed processor was chosen as the most promising technology and several encouraging test runs were conducted. This technology continues to be very promising in producing low cost polysilicon. The Union Carbide silane process and the research development on the fluidized bed silane decomposition are discussed.

Doping of wide-bandgap titanium-dioxide nanotubes: optical, electronic and magnetic properties

Science.gov (United States)

Alivov, Yahya; Singh, Vivek; Ding, Yuchen; Cerkovnik, Logan Jerome; Nagpal, Prashant

2014-08-01

Doping semiconductors is an important step for their technological application. While doping bulk semiconductors can be easily achieved, incorporating dopants in semiconductor nanostructures has proven difficult. Here, we report a facile synthesis method for doping titanium-dioxide (TiO2) nanotubes that was enabled by a new electrochemical cell design. A variety of optical, electronic and magnetic dopants were incorporated into the hollow nanotubes, and from detailed studies it is shown that the doping level can be easily tuned from low to heavily-doped semiconductors. Using desired dopants - electronic (p- or n-doped), optical (ultraviolet bandgap to infrared absorption in co-doped nanotubes), and magnetic (from paramagnetic to ferromagnetic) properties can be tailored, and these technologically important nanotubes can be useful for a variety of applications in photovoltaics, display technologies, photocatalysis, and spintronic applications.Doping semiconductors is an important step for their technological application. While doping bulk semiconductors can be easily achieved, incorporating dopants in semiconductor nanostructures has proven difficult. Here, we report a facile synthesis method for doping titanium-dioxide (TiO2) nanotubes that was enabled by a new electrochemical cell design. A variety of optical, electronic and magnetic dopants were incorporated into the hollow nanotubes, and from detailed studies it is shown that the doping level can be easily tuned from low to heavily-doped semiconductors. Using desired dopants - electronic (p- or n-doped), optical (ultraviolet bandgap to infrared absorption in co-doped nanotubes), and magnetic (from paramagnetic to ferromagnetic) properties can be tailored, and these technologically important nanotubes can be useful for a variety of applications in photovoltaics, display technologies, photocatalysis, and spintronic applications. Electronic supplementary information (ESI) available: See DOI: 10.1039/c4nr02417f

System Dynamics of Polysilicon for Solar Photovoltaics: A Framework for Investigating the Energy Security of Renewable Energy Supply Chains

Directory of Open Access Journals (Sweden)

Debra Sandor

2018-01-01

Full Text Available Renewable energy, produced with widely available low-cost energy resources, is often included as a component of national strategies to address energy security and sustainability. Market and political forces cannot disrupt the sun or wind, unlike oil and gas supplies. However, the cost of renewable energy is highly dependent on technologies manufactured through global supply chains in leading manufacturing countries. The countries that contribute to the global supply chains may take actions that, directly or indirectly, influence global access to materials and components. For example, high-purity polysilicon, a key material in solar photovoltaics, has experienced significant price fluctuations, affecting the manufacturing capacity and cost of both polysilicon and solar panels. This study developed and validated an initial system dynamics framework to gain insights into global trade in polysilicon. The model represents an initial framework for exploration. Three regions were modeled—China, the United States, and the rest of the world—for a range of trade scenarios to understand the impacts of import duties and non-price drivers on the relative volumes of imports and domestic supply. The model was validated with the historical case of China imposing an import duty on polysilicon from the United States, the European Union, and South Korea, which altered the regional flows of polysilicon—in terms of imports, exports, and domestic production—to varying degrees. As expected, the model tracked how regional demand shares and influx volumes decrease as a duty on a region increases. Using 2016 as a reference point, in the scenarios examined for U.S. exports to China, each 10% increase in the import duty results in a 40% decrease in import volume. The model also indicates that, under the scenarios investigated, once a duty has been imposed on a region, the demand share from that region declines and does not achieve pre-duty levels, even as global

Boron-doped nanodiamonds as possible agents for local hyperthermia

Science.gov (United States)

Vervald, A. M.; Burikov, S. A.; Vlasov, I. I.; Ekimov, E. A.; Shenderova, O. A.; Dolenko, T. A.

2017-04-01

In this work, the effective heating of surrounding water by heavily-boron-doped nanodiamonds (NDs) under laser irradiation of visible wavelength was found. Using Raman scattering spectroscopy of aqueous suspensions of boron-doped NDs, it was found that this abnormally high heating results in the weakening of hydrogen bonds much more so (2-5 times stronger) than for undoped NDs. The property of boron-doped NDs to heat a solvent under the influence of laser radiation (1-5 W cm-2) opens broad prospects for their use to create nanoagents for medical oncology and local hyperthermia.

Hydrogen-boron complexes in heavily boron-doped silicon treated with high concentration of hydrogen atoms

International Nuclear Information System (INIS)

Fukata, N.; Fukuda, S.; Sato, S.; Ishioka, K.; Kitajima, M.; Hishita, S.; Murakami, K.

2006-01-01

The formation of hydrogen (H)-related complexes was investigated in boron (B)-doped Si treated with high concentration of H. The isotope shifts of H-related Raman peaks by replacement of H to deuterium and 1 B to 11 B clearly showed the formation of the B-H complexes in which H directly bonds to B in Si. The results of the resistivity measurements suggested that the B acceptors are passivated via the formation of the B-H complexes, as well as the well-known passivation center in B-doped Si, namely, H-B passivation center

Proton irradiation induced defects in Cd and Zn doped InP

International Nuclear Information System (INIS)

Rybicki, G.C.; Williams, W.S.

1993-01-01

Proton irradiation induced defects in Zn and Cd doped InP have been studied by deep level transient spectroscopy, (DLTS). After 2 MeV proton irradiation the defects H4 and H5 were observed in lightly Zn doped InP, while the defects H3 and H5 were observed in more heavily Zn and Cd doped InP. The defect properties were not affected by the substitution of Cd for Zn, but the introduction rate of H5 was lower in Cd doped InP. The annealing rate of defects was also higher in Cd doped InP. The use of Cd doped InP may thus result in an InP solar cell with even greater radiation resistance

Numerical analysis of a polysilicon-based resistive memory device

KAUST Repository

Berco, Dan

2018-03-08

This study investigates a conductive bridge resistive memory device based on a Cu top electrode, 10-nm polysilicon resistive switching layer and a TiN bottom electrode, by numerical analysis for $$10^{3}$$103 programming and erase simulation cycles. The low and high resistive state values in each cycle are calculated, and the analysis shows that the structure has excellent retention reliability properties. The presented Cu species density plot indicates that Cu insertion occurs almost exclusively along grain boundaries resulting in a confined isomorphic conductive filament that maintains its overall shape and electric properties during cycling. The superior reliability of this structure may thus be attributed to the relatively low amount of Cu migrating into the RSL during initial formation. In addition, the results show a good match and help to confirm experimental measurements done over a previously demonstrated device.

Insertion of a pentacene layer into the gold/poly(methyl methacrylate)/heavily doped p-type Si/indium device leading to the modulation of resistive switching characteristics

Science.gov (United States)

Hung, Cheng-Chun; Lin, Yow-Jon

2018-01-01

In order to get a physical insight into the pentacene interlayer-modulated resistive switching (RS) characteristics, the Au/pentacene/poly(methyl methacrylate) (PMMA)/heavily doped p-type Si (p+-Si)/In and Au/PMMA/p+-Si/In devices are fabricated and the device performance is provided. The Au/pentacene/PMMA/p+-Si/In device shows RS behavior, whereas the Au/PMMA/p+-Si/In device exhibits the set/reset-free hysteresis current-voltage characteristics. The insertion of a pentacene layer is a noticeable contribution to the RS characteristic. This is because of the occurrence of carrier accumulation/depletion in the pentacene interlayer. The transition from carrier depletion to carrier accumulation (carrier accumulation to carrier depletion) in pentacene occurring under negative (positive) voltage induces the process of set (reset). The switching conduction mechanism is primarily described as space charge limited conduction according to the electrical transport properties measurement. The concept of a pentacene/PMMA heterostructure opens a promising direction for organic memory devices.

Electrical property studies of neutron-transmutation-doped silicon

International Nuclear Information System (INIS)

Cleland, J.W.; Fleming, P.H.; Westbrook, R.D.; Wood, R.F.; Young, R.T.

1978-01-01

Results of studies of electrical properties of neutron-transmutation-doped (NTD) silicon are presented. Annealing requirements to remove lattice damage were obtained. The electrical role of clustered oxygen and defect-oxygen complex was investigated. An NTD epitaxial layer on a heavily doped n- or p- type substrate can be produced. There is no evident interaction between lithium introduced by diffusion and phosphorous 31 introduced by irradiation. There may be some type of pairing reaction between lithium 7 introduced by boron 10 fission and any remaining boron

Thermal diffusion boron doping of single-crystal natural diamond

Energy Technology Data Exchange (ETDEWEB)

Seo, Jung-Hun; Mikael, Solomon; Mi, Hongyi; Venkataramanan, Giri; Ma, Zhenqiang, E-mail: mazq@engr.wisc.edu [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Wu, Henry; Morgan, Dane [Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Blanchard, James P. [Department of Nuclear Engineering and Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Zhou, Weidong [Department of Electrical Engineering, NanoFAB Center, University of Texas at Arlington, Arlington, Texas 76019 (United States); Gong, Shaoqin [Department of Biomedical Engineering and Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

2016-05-28

With the best overall electronic and thermal properties, single crystal diamond (SCD) is the extreme wide bandgap material that is expected to revolutionize power electronics and radio-frequency electronics in the future. However, turning SCD into useful semiconductors requires overcoming doping challenges, as conventional substitutional doping techniques, such as thermal diffusion and ion implantation, are not easily applicable to SCD. Here we report a simple and easily accessible doping strategy demonstrating that electrically activated, substitutional doping in SCD without inducing graphitization transition or lattice damage can be readily realized with thermal diffusion at relatively low temperatures by using heavily doped Si nanomembranes as a unique dopant carrying medium. Atomistic simulations elucidate a vacancy exchange boron doping mechanism that occurs at the bonded interface between Si and diamond. We further demonstrate selectively doped high voltage diodes and half-wave rectifier circuits using such doped SCD. Our new doping strategy has established a reachable path toward using SCDs for future high voltage power conversion systems and for other novel diamond based electronic devices. The novel doping mechanism may find its critical use in other wide bandgap semiconductors.

Thermal diffusion boron doping of single-crystal natural diamond

International Nuclear Information System (INIS)

Seo, Jung-Hun; Mikael, Solomon; Mi, Hongyi; Venkataramanan, Giri; Ma, Zhenqiang; Wu, Henry; Morgan, Dane; Blanchard, James P.; Zhou, Weidong; Gong, Shaoqin

2016-01-01

With the best overall electronic and thermal properties, single crystal diamond (SCD) is the extreme wide bandgap material that is expected to revolutionize power electronics and radio-frequency electronics in the future. However, turning SCD into useful semiconductors requires overcoming doping challenges, as conventional substitutional doping techniques, such as thermal diffusion and ion implantation, are not easily applicable to SCD. Here we report a simple and easily accessible doping strategy demonstrating that electrically activated, substitutional doping in SCD without inducing graphitization transition or lattice damage can be readily realized with thermal diffusion at relatively low temperatures by using heavily doped Si nanomembranes as a unique dopant carrying medium. Atomistic simulations elucidate a vacancy exchange boron doping mechanism that occurs at the bonded interface between Si and diamond. We further demonstrate selectively doped high voltage diodes and half-wave rectifier circuits using such doped SCD. Our new doping strategy has established a reachable path toward using SCDs for future high voltage power conversion systems and for other novel diamond based electronic devices. The novel doping mechanism may find its critical use in other wide bandgap semiconductors.

An In0.52Al0.48As/n+-In0.53Ga0.47As MISFET with a modulation-doped channel

International Nuclear Information System (INIS)

DelAlamo, J.A.

1989-01-01

A heterostructure metal-insulator-semiconductor field-effect transistor (MISFET) with a modulation-doped channel is proposed. In this device, a very thin undoped subchannel is located between the undoped wide-bandgap insulator and a thin heavily doped channel. In the depletion mode of operation, electron transport takes place along the heavily doped channel. When the device enters the accumulation mode of operation, electrons pile up against the heterointerface in the high-mobility undoped subchannel. This should result in markedly improved transport characteristics at the onset of accumulation. The concept is demonstrated in the In 0.52 Al 0.48 As/In 0.53 Ga 0.47 As system on InP

Self-Heating Effects In Polysilicon Source Gated Transistors

Science.gov (United States)

Sporea, R. A.; Burridge, T.; Silva, S. R. P.

2015-01-01

Source-gated transistors (SGTs) are thin-film devices which rely on a potential barrier at the source to achieve high gain, tolerance to fabrication variability, and low series voltage drop, relevant to a multitude of energy-efficient, large-area, cost effective applications. The current through the reverse-biased source barrier has a potentially high positive temperature coefficient, which may lead to undesirable thermal runaway effects and even device failure through self-heating. Using numerical simulations we show that, even in highly thermally-confined scenarios and at high current levels, self-heating is insufficient to compromise device integrity. Performance is minimally affected through a modest increase in output conductance, which may limit the maximum attainable gain. Measurements on polysilicon devices confirm the simulated results, with even smaller penalties in performance, largely due to improved heat dissipation through metal contacts. We conclude that SGTs can be reliably used for high gain, power efficient analog and digital circuits without significant performance impact due to self-heating. This further demonstrates the robustness of SGTs. PMID:26351099

Photovoltaic investigation of minority carrier lifetime in the heavily-doped emitter layer of silicon junction solar cell

Science.gov (United States)

Ho, C.-T.

1982-01-01

The results of experiments on the recombination lifetime in a phosphorus diffused N(+) layer of a silicon solar cell are reported. The cells studied comprised three groups of Czochralski grown crystals: boron doped to one ohm-cm, boron doped to 6 ohm-cm, and aluminum doped to one ohm-cm, all with a shunt resistance exceeding 500 kilo-ohms. The characteristic bulk diffusion length of a cell sample was determined from the short circuit current response to light at a wavelength of one micron. The recombination rates were obtained by measurement of the open circuit voltage as a function of the photogeneration rate. The recombination rate was found to be dependent on the photoinjection level, and is positive-field controlled at low photoinjection, positive-field influence Auger recombination at a medium photoinjection level, and negative-field controlled Auger recombination at a high photoinjection level.

Different annealing temperature suitable for different Mg doped P-GaN

Science.gov (United States)

Liu, S. T.; Yang, J.; Zhao, D. G.; Jiang, D. S.; Liang, F.; Chen, P.; Zhu, J. J.; Liu, Z. S.; Li, X.; Liu, W.; Zhang, L. Q.; Long, H.; Li, M.

2017-04-01

In this work, epitaxial GaN with different Mg doping concentration annealed at different temperature is investigated. Through Hall and PL spectra measurement we found that when Mg doping concentration is different, different annealing temperature is needed for obtaining the best p-type conduction of GaN, and this difference comes from the different influence of annealing on compensated donors. For ultra-heavily Mg doped sample, the process of Mg related donors transferring to non-radiative recombination centers is dominated, so the performance of P-GaN deteriorates with temperature increase. But for low Mg doped sample, the process of Mg related donors transfer to non-raditive recombination is weak compare to the Mg acceptor activation, so along the annealing temperature increase the performance GaN gets better.

Simulation of new p-type strip detectors with trench to enhance the charge multiplication effect in the n-type electrodes

International Nuclear Information System (INIS)

Fernández-Martínez, P.; Pellegrini, G.; Balbuena, J.P.; Quirion, D.; Hidalgo, S.; Flores, D.; Lozano, M.; Casse, G.

2011-01-01

This paper shows the simulation results of new p-type strip detectors with trench electrodes to enhance the charge multiplication effect in the irradiated detector. The new design includes baby microstrip detectors (area=1 cm 2 ) with a strip pitch of 80 μm and p-stop isolation structures. The strip has a 5 μm-wide trench along all its length, filled and doped with polysilicon to create a deep N + contact into the material bulk. The trench depth can be varied in order to study the influence of the electric field on the charge multiplication effect in heavily irradiated samples. Some alternative designs have also been studied to establish a comparison between various structures using different technologies. Simulation reproduce the electrical behaviour under different irradiation conditions, taking into account the damage accumulated after irradiation with neutrons and protons with several fluence values. The investigation of these effects provides important indications on the ability of this modified electrode geometry to control and optimise the charge multiplication effect, in order to fully recover the collection efficiency of heavily irradiated microstrip detectors, at reasonable bias voltage compatible with the voltage feed limitation of the CERN SLHC experiments.

Application of an improved band-gap narrowing model to the numerical simulation of recombination properties of phosphorus-doped silicon emitters

Energy Technology Data Exchange (ETDEWEB)

Schumacher, J.O. [Fraunhofer Institute for Solar Energy Systems ISE, Oltmannsstr, 5, D-79100 Freiburg (Germany); Altermatt, P.P.; Heiser, G.; Aberle, A.G. [Photovoltaics Special Research Centre, University of NSW, 2052 Sydney (Australia)

2001-01-01

The commonly used band-gap narrowing (BGN) models for crystalline silicon do not describe heavily doped emitters with desirable precision. One of the reasons for this is that the applied BGN models were empirically derived from measurements assuming Boltzmann statistics. We apply a new BGN model derived by Schenk from quantum mechanical principles and demonstrate that carrier degeneracy and the new BGN model both substantially affect the electron-hole product within the emitter region. Simulated saturation current densities of heavily phosphorus-doped emitters, calculated with the new BGN model, are lower than results obtained with the widely used empirical BGN model of del Alamo.

Evolution of titanium residue on the walls of a plasma-etching reactor and its effect on the polysilicon etching rate

Energy Technology Data Exchange (ETDEWEB)

Hirota, Kosa, E-mail: hirota-kousa@sme.hitachi-hitec.com; Itabashi, Naoshi; Tanaka, Junichi [Hitachi, Ltd., Central Research Laboratory, 1-280, Higashi-Koigakubo, Kokubunji, Tokyo 185-8601 (Japan)

2014-11-01

The variation in polysilicon plasma etching rates caused by Ti residue on the reactor walls was investigated. The amount of Ti residue was measured using attenuated total reflection Fourier transform infrared spectroscopy with the HgCdTe (MCT) detector installed on the side of the reactor. As the amount of Ti residue increased, the number of fluorine radicals and the polysilicon etching rate increased. However, a maximum limit in the etching rate was observed. A mechanism of rate variation was proposed, whereby F radical consumption on the quartz reactor wall is suppressed by the Ti residue. The authors also investigated a plasma-cleaning method for the removal of Ti residue without using a BCl{sub 3} gas, because the reaction products (e.g., boron oxide) on the reactor walls frequently cause contamination of the product wafers during etching. CH-assisted chlorine cleaning, which is a combination of CHF{sub 3} and Cl{sub 2} plasma treatment, was found to effectively remove Ti residue from the reactor walls. This result shows that CH radicals play an important role in deoxidizing and/or defluorinating Ti residue on the reactor walls.

Simulation of Heavily Irradiated Silicon Pixel Sensors and Comparison with Test Beam Measurements

CERN Document Server

Chiochia, Vincenzo; Bortoletto, Daniela; Cremaldi, Lucien; Cucciarelli, Susanna; Dorokhov, Andrei; Hoermann, Christoph; Kim, Dongwook; Konecki, Marcin; Kotlinski, Danek; Prokofiev, Kirill; Regenfus, Christian; Rohe, Tilman; Sanders, David A.; Son, Seunghee; Speer, Thomas; Chiochia, Vincenzo; Swartz, Morris; Bortoletto, Daniela; Cremaldi, Lucien; Cucciarelli, Susanna; Dorokhov, Andrei; Hoermann, Christoph; Kim, Dongwook; Konecki, Marcin; Kotlinski, Danek; Prokofiev, Kirill; Regenfus, Christian; Rohe, Tilman; Sanders, David A.; Son, Seunghee; Speer, Thomas

2004-01-01

Charge collection measurements performed on heavily irradiated p-spray DOFZ pixel sensors with a grazing angle hadron beam provide a sensitive determination of the electric field within the detectors. The data are compared with a complete charge transport simulation of the sensor which includes signal trapping and charge induction effects. A linearly varying electric field based upon the standard picture of a constant type-inverted effective doping density is inconsistent with the data. A two-trap double junction model implemented in the ISE TCAD software can be tuned to produce a doubly-peaked electric field which describes the data reasonably well. The modeled field differs somewhat from previous determinations based upon the transient current technique. The model can also account for the level of charge trapping observed in the data.

Excimer laser doping technique for application in an integrated CdTe imaging device

CERN Document Server

Mochizuki, D; Aoki, T; Tomita, Y; Nihashi, T; Hatanaka, Y

1999-01-01

CdTe is an attractive semiconductor material for applications in solid-state high-energy X-ray and gamma-ray imaging systems because of its high absorption coefficient, large band gap, good mobility lifetime product of holes and stability at normal atmospheric conditions. We propose a new concept for fabricating an integrated CdTe with monolithic circuit configuration for two-dimensional imaging systems suitable for medical, research or industrial applications and operation at room temperature. A new doping technique has been recently developed that employs excimer laser radiation to diffuse impurity atoms into the semiconductor. Accordingly, heavily doped n- and p-type layers with resistivities less than 1 OMEGA cm can be formed on the high resistive CdTe crystals. We have further extended this technique for doping with spatial pattern. We will present the laser doping technique and various results thus obtained. Spatially patterned doping is demonstrated and we propose the use of these doping techniques for...

Challenges and threats to implementing the fight against doping in sport.

Science.gov (United States)

Dvorak, Jiri; Saugy, Martial; Pitsiladis, Yannis P

2014-05-01

Prominent doping cases in certain sports have recently raised public awareness of doping and reinforced the perception that doping is widespread. Efforts to deal with doping in sport have intensified in recent years, yet the general public believes that the 'cheaters' are ahead of the testers. Therefore, there is an urgent need to change the antidoping strategy. For example, the increase in the number of individual drug tests conducted between 2005 and 2012 was approximately 90 000 and equivalent to an increase of about 50%, yet the number of adverse analytical findings remained broadly the same. There is also a strikingly different prevalence of doping substances and methods in sports such as a 0.03% prevalence of anabolic steroids in football compared to 0.4% in the overall WADA statistics. Future efforts in the fight against doping should therefore be more heavily based on preventative strategies such as education and on the analysis of data and forensic intelligence and also on the experiences of relevant stakeholders such as the national antidoping organisations, the laboratories, athletes or team physicians and related biomedical support staff. This strategy is essential to instigate the change needed to more effectively fight doping in sport.

Electrical activation of nitrogen heavily implanted 3C-SiC(1 0 0)

Energy Technology Data Exchange (ETDEWEB)

Li, Fan, E-mail: f.li.1@warwick.ac.uk [School of Engineering, University of Warwick, Coventry CV4 7AL (United Kingdom); Sharma, Yogesh; Shah, Vishal; Jennings, Mike [School of Engineering, University of Warwick, Coventry CV4 7AL (United Kingdom); Pérez-Tomás, Amador [ICN2 – Institut Catala de Nanociència i Nanotecnologia, Campus UAB, 08193 Bellaterra, Barcelona (Spain); Myronov, Maksym [Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom); Fisher, Craig [School of Engineering, University of Warwick, Coventry CV4 7AL (United Kingdom); Leadley, David [Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom); Mawby, Phil [School of Engineering, University of Warwick, Coventry CV4 7AL (United Kingdom)

2015-10-30

Highlights: • Nitrogen is fully activated by 1175 °C annealing for 1.5 × 10{sup 19} cm{sup −3} doped 3C-SiC. • Free donor concentration is found to readily saturate in 3C-SiC at ∼7 × 10{sup 19} cm{sup −3}. • 3C-SiC is found to have complete donor thermal ionization above 150 K. • Donor in 1.5 × 10{sup 19} cm{sup −3} nitrogen implanted 3C-SiC has an energy level ∼15 meV. • The SiO{sub 2} cap is found to have a bigger influence on low and medium doped samples. - Abstract: A degenerated wide bandgap semiconductor is a rare system. In general, implant levels lie deeper in the band-gap and carrier freeze-out usually takes place at room temperature. Nevertheless, we have observed that heavily doped n-type degenerated 3C-SiC films are achieved by nitrogen implantation level of ∼6 × 10{sup 20} cm{sup −3} at 20 K. According to temperature dependent Hall measurements, nitrogen activation rates decrease with the doping level from almost 100% (1.5 × 10{sup 19} cm{sup −3}, donor level 15 meV) to ∼12% for 6 × 10{sup 20} cm{sup −3}. Free donors are found to saturate in 3C-SiC at ∼7 × 10{sup 19} cm{sup −3}. The implanted film electrical performances are characterized as a function of the dopant doses and post implantation annealing (PIA) conditions by fabricating Van der Pauw structures. A deposited SiO{sub 2} layer was used as the surface capping layer during the PIA process to study its effect on the resultant film properties. From the device design point of view, the lowest sheet resistivity (∼1.4 mΩ cm) has been observed for medium doped (4 × 10{sup 19} cm{sup −3}) sample with PIA 1375 °C 2 h without a SiO{sub 2} cap.

Gas Nozzle Effect on the Deposition of Polysilicon by Monosilane Siemens Reactor

Directory of Open Access Journals (Sweden)

Seung Oh Kang

2012-01-01

Full Text Available Deposition of polysilicon (poly-Si was tried to increase productivity of poly-Si by using two different types of gas nozzle in a monosilane Bell-jar Siemens (MS-Siemens reactor. In a mass production of poly-Si, deposition rate and energy consumption are very important factors because they are main performance indicators of Siemens reactor and they are directly related with the production cost of poly-Si. Type A and B nozzles were used for investigating gas nozzle effect on the deposition of poly-Si in a MS-Siemens reactor. Nozzle design was analyzed by computation cluid dynamics (CFD. Deposition rate and energy consumption of poly-Si were increased when the type B nozzle was used. The highest deposition rate was 1 mm/h, and the lowest energy consumption was 72 kWh⋅kg-1 in this study.

Spin-Glass Transition and Giant Paramagnetism in Heavily Hole-Doped Bi2Sr2Co2Oy

Science.gov (United States)

Hsu, Hung Chang; Lee, Wei-Li; Lin, Jiunn-Yuan; Young, Ben-Li; Kung, Hsiang-Hsi; Huang, Jian; Chou, Fang Cheng

2014-02-01

Hole-doped single crystals of misfit-layered cobaltate Bi2-xPbxSr2-zCo2Oy (x = 0-0.61, y = 8.28-8.62, and z = 0.01-0.22) have been successfully grown using the optical floating-zone method. Heavier hole doping has been achieved through both Pb substitution in the Bi site and the more effective Sr vacancy formation. The Co4+ : Co3+ ratio can be raised significantly from its original ˜1 : 1 to 4.5 : 1, as confirmed by iodometric titration. A spin-glass transition temperature of Tg ˜ 70 K is confirmed by ac susceptibility measurement when the Co4+ : Co3+ ratio becomes higher than 2 : 1, presumably owing to the significantly increased probability of triangular geometrical frustration among antiferromagnetically coupled localized Co4+ spins.

Extended X-ray absorption fine structure studies of impulsive-type hardening in the heavily Be-doped ZnSe ternaries

Energy Technology Data Exchange (ETDEWEB)

Khan, Shabina; Singh, Pankaja [Barkatullah University, Bhopal (India); Mazher, Javed [Addis Ababa University, Addis Ababa (Ethiopia)

2014-02-15

Inherently soft zinc-selenides have been hardened through beryllium doping. High-quality stoichiometric ternaries of Be{sub x}Zn{sub 1-x}Se have been synthesized by using the Bridgeman technique. State-of-art X-ray absorption spectroscopy is performed by varying the concentration of the cationic dopant, Be, from 6% to 55% in the host ZnSe. Extended X-ray absorption fine structure analyses are carried out to study the next-neighbor and next nearest neighbor atomic positions, nature of the substitutional doping, extent of bond length homogeneity, the presence of involuntary contrast among path distances, and the crossover from a soft to a hard character of the ternary with increasing Be concentration. Our results indicate the presence of a non-regular impulsive hardening in the ternary with a disparity at the lower and the higher Be-doping levels, which are discussed vis-a-vis self-accommodation of substitutional dopants in the host lattice.

Observation of an electron band above the Fermi level in FeTe0.55Se0.45 from in-situ surface doping

International Nuclear Information System (INIS)

Zhang, P.; Ma, J.; Qian, T.; Richard, P.; Ding, H.; Xu, N.; Xu, Y.-M.; Fedorov, A. V.; Denlinger, J. D.; Gu, G. D.

2014-01-01

We used in-situ potassium (K) evaporation to dope the surface of the iron-based superconductor FeTe 0.55 Se 0.45 . The systematic study of the bands near the Fermi level confirms that electrons are doped into the system, allowing us to tune the Fermi level of this material and to access otherwise unoccupied electronic states. In particular, we observe an electron band located above the Fermi level before doping that shares similarities with a small three-dimensional pocket observed in the cousin, heavily electron-doped KFe 2−x Se 2 compound.

Effect of Mg Doping on the Photoluminescence of GaN:Mg Films by Radio-Frequency Plasma-Assisted Molecular Beam Epitaxy

International Nuclear Information System (INIS)

Sui Yan-Ping; Yu Guang-Hui

2011-01-01

We investigate undoped GaN and Mg-doped GaN grown by rf plasma-assisted molecular beam epitaxy (MBE) with different Mg concentrations by photoluminescence (PL) at low temperature, Hall-effect and XRD measurements. In the PL spectra of lightly Mg-doped GaN films, a low intensity near band edge (NBE) emission and strong donor-acceptor pair (DAP) emission with its phonon replicas are observed. As the Mg concentration is increased, the DAP and NBE bands become weaker and a red shift of these bands is observed in the PL spectra. Yellow luminescence (YL) is observed in heavily Mg-doped GaN. The x-ray diffraction is employed to study the structure of the films. Hall measurement shows that there is a maximum value (3.9 × 10 18 cm −3 ) of hole concentration with increasing Mg source temperature for compensation effect. PL spectra of undoped GaN are also studied under N-rich and Ga-rich growth conditions. Yellow luminescences of undoped Ga-rich GaN and heavily Mg-doped GaN are compared, indicating the different origins of the YL bands. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Design and Modeling of Polysilicon Electrothermal Actuators for a MEMS Mirror with Low Power Consumption

Directory of Open Access Journals (Sweden)

Miguel Lara-Castro

2017-06-01

Full Text Available Endoscopic optical-coherence tomography (OCT systems require low cost mirrors with small footprint size, out-of-plane deflections and low bias voltage. These requirements can be achieved with electrothermal actuators based on microelectromechanical systems (MEMS. We present the design and modeling of polysilicon electrothermal actuators for a MEMS mirror (100 μm × 100 μm × 2.25 μm. These actuators are composed by two beam types (2.25 μm thickness with different cross-section area, which are separated by 2 μm gap. The mirror and actuators are designed through the Sandia Ultra-planar Multi-level MEMS Technology V (SUMMiT V® process, obtaining a small footprint size (1028 μm × 1028 µm for actuators of 550 µm length. The actuators have out-of-plane displacements caused by low dc voltages and without use material layers with distinct thermal expansion coefficients. The temperature behavior along the actuators is calculated through analytical models that include terms of heat energy generation, heat conduction and heat energy loss. The force method is used to predict the maximum out-of-plane displacements in the actuator tip as function of supplied voltage. Both analytical models, under steady-state conditions, employ the polysilicon resistivity as function of the temperature. The electrothermal-and structural behavior of the actuators is studied considering different beams dimensions (length and width and dc bias voltages from 0.5 to 2.5 V. For 2.5 V, the actuator of 550 µm length reaches a maximum temperature, displacement and electrical power of 115 °C, 10.3 µm and 6.3 mW, respectively. The designed actuation mechanism can be useful for MEMS mirrors of different sizes with potential application in endoscopic OCT systems that require low power consumption.

Chemical state analysis of heavily phosphorus-doped epitaxial silicon films grown on Si (1 0 0) by X-ray photoelectron spectroscopy

Science.gov (United States)

Lee, Minhyeong; Kim, Sungtae; Ko, Dae-Hong

2018-06-01

In this work, we investigated the chemical bonding states in highly P-doped Si thin films epitaxially grown on Si (0 0 1) substrates using high-resolution X-ray photoelectron spectroscopy (HR-XPS). HR-XPS P 2p core-level spectra clearly show spin-orbital splitting between P 2p1/2 and P 2p3/2 peaks in Si films doped with a high concentration of P. Moreover, the intensities of P 2p1/2 and P 2p3/2 peaks for P-doped Si films increase with P concentrations, while their binding energies remained almost identical. These results indicate that more P atoms are incorporated into the substitutional sites of the Si lattice with the increase of P concentrations. In order to identify the chemical states of P-doped Si films shown in XPS Si 2p spectra, the spectra of bulk Si were subtracted from those of Si:P samples, which enables us to clearly identify the new chemical state related to Sisbnd P bonds. We observed that the presence of the two well-resolved new peaks only for the Si:P samples at the binding energy higher than those of a Sisbnd Si bond, which is due to the strong electronegativity of P than that of Si. Experimental findings in this study using XPS open up new doors for evaluating the chemical states of P-doped Si materials in fundamental researches as well as in industrial applications.

Fabrication Effects on Polysilicon-based Micro cantilever Piezo resistivity for Biological Sensing Application

International Nuclear Information System (INIS)

Nina Korlina Madzhi; Balkish Natra; Mastura Sidek; Khuan, L.Y.; Anuar Ahmad

2011-01-01

In principle, adsorption of biological molecules on a functionalized surface of a micro fabricated cantilever will cause a surface stress and consequently the cantilever bending. In this work, four different type of polysilicon-based piezo resistive micro cantilever sensors were designed to increase the sensitivity of the micro cantilevers sensor because the forces involved is very small. The design and optimization was performed by using finite element analysis to maximize the relative resistance changes of the piezo resistors as a function of the cantilever vertical displacements. The resistivity of the piezo resistivity micro cantilevers was analyzed before and after dicing process. The maximum resistance changes were systematically investigated by varying the piezo resistor length. The results show that although the thickness of piezo resistor was the same at 0.5 μm the resistance value was varied. (author)

A Solution-Doped Polymer Semiconductor:Insulator Blend for Thermoelectrics

KAUST Repository

Kiefer, David; Yu, Liyang; Fransson, Erik; Gó mez, André s; Primetzhofer, Daniel; Amassian, Aram; Campoy-Quiles, Mariano; Mü ller, Christian

2016-01-01

Poly(ethylene oxide) is demonstrated to be a suitable matrix polymer for the solution-doped conjugated polymer poly(3-hexylthiophene). The polarity of the insulator combined with carefully chosen processing conditions permits the fabrication of tens of micrometer-thick films that feature a fine distribution of the F4TCNQ dopant:semiconductor complex. Changes in electrical conductivity from 0.1 to 0.3 S cm−1 and Seebeck coefficient from 100 to 60 μV K−1 upon addition of the insulator correlate with an increase in doping efficiency from 20% to 40% for heavily doped ternary blends. An invariant bulk thermal conductivity of about 0.3 W m−1 K−1 gives rise to a thermoelectric Figure of merit ZT ∼ 10−4 that remains unaltered for an insulator content of more than 60 wt%. Free-standing, mechanically robust tapes illustrate the versatility of the developed dopant:semiconductor:insulator ternary blends.

A Solution-Doped Polymer Semiconductor:Insulator Blend for Thermoelectrics

KAUST Repository

Kiefer, David

2016-09-01

Poly(ethylene oxide) is demonstrated to be a suitable matrix polymer for the solution-doped conjugated polymer poly(3-hexylthiophene). The polarity of the insulator combined with carefully chosen processing conditions permits the fabrication of tens of micrometer-thick films that feature a fine distribution of the F4TCNQ dopant:semiconductor complex. Changes in electrical conductivity from 0.1 to 0.3 S cm−1 and Seebeck coefficient from 100 to 60 μV K−1 upon addition of the insulator correlate with an increase in doping efficiency from 20% to 40% for heavily doped ternary blends. An invariant bulk thermal conductivity of about 0.3 W m−1 K−1 gives rise to a thermoelectric Figure of merit ZT ∼ 10−4 that remains unaltered for an insulator content of more than 60 wt%. Free-standing, mechanically robust tapes illustrate the versatility of the developed dopant:semiconductor:insulator ternary blends.

Compensation and persistent photocapacitance in homoepitaxial Sn-doped β-Ga2O3

Science.gov (United States)

Polyakov, A. Y.; Smirnov, N. B.; Shchemerov, I. V.; Gogova, D.; Tarelkin, S. A.; Pearton, S. J.

2018-03-01

The electrical properties of epitaxial β-Ga2O3 doped with Sn (1016-9 × 1018 cm-3) and grown by metalorganic chemical vapor deposition on semi-insulating β-Ga2O3 substrates are reported. Shallow donors attributable to Sn were observed only in a narrow region near the film/substrate interface and with a much lower concentration than the total Sn density. For heavily Sn doped films (Sn concentration, 9 × 1018 cm-3), the electrical properties in the top portion of the layer were determined by deep centers with a level at Ec-0.21 eV not described previously. In more lightly doped layers, the Ec-0.21 eV centers and deeper traps at Ec-0.8 eV were present, with the latter pinning the Fermi level. Low temperature photocapacitance and capacitance voltage measurements of illuminated samples indicated the presence of high densities (1017-1018 cm-3) of deep acceptors with an optical ionization threshold of 2.3 eV. Optical deep level transient spectroscopy (ODLTS) and photoinduced current transient spectroscopy (PICTS) detected electron traps at Ec-0.8 eV and Ec-1.1 eV. For lightly doped layers, the compensation of film conductivity was mostly provided by the Ec-2.3 eV acceptors. For heavily Sn doped films, deep acceptor centers possibly related to Ga vacancies were significant. The photocapacitance and the photocurrent caused by illumination at low temperatures were persistent, with an optical threshold of 1.9 eV and vanished only at temperatures of ˜400 K. The capture barrier for electrons causing the persistent photocapacitance effect was estimated from ODLTS and PICTS to be 0.25-0.35 eV.

Optical Gaps in Pristine and Heavily Doped Silicon Nanocrystals: DFT versus Quantum Monte Carlo Benchmarks.

Science.gov (United States)

Derian, R; Tokár, K; Somogyi, B; Gali, Á; Štich, I

2017-12-12

We present a time-dependent density functional theory (TDDFT) study of the optical gaps of light-emitting nanomaterials, namely, pristine and heavily B- and P-codoped silicon crystalline nanoparticles. Twenty DFT exchange-correlation functionals sampled from the best currently available inventory such as hybrids and range-separated hybrids are benchmarked against ultra-accurate quantum Monte Carlo results on small model Si nanocrystals. Overall, the range-separated hybrids are found to perform best. The quality of the DFT gaps is correlated with the deviation from Koopmans' theorem as a possible quality guide. In addition to providing a generic test of the ability of TDDFT to describe optical properties of silicon crystalline nanoparticles, the results also open up a route to benchmark-quality DFT studies of nanoparticle sizes approaching those studied experimentally.

Characteristic of doping and diffusion of heavily doped n and p type InP and InGaAs epitaxial layers grown by metal organic chemical vapor deposition

International Nuclear Information System (INIS)

Pinzone, C.J.; Dupuis, R.D.; Ha, N.T.; Luftman, H.S.; Gerrard, N.D.

1990-01-01

Electronic and photonic device applications of the InGaAs/InP materials system often require the growth of epitaxial material doped to or near the solubility limit of the impurity in the host material. These requirements present an extreme challenge for the crystal grower. To produce devices with abrupt dopant profiles, preserve the junction during subsequent growth, and retain a high degree of crystalline perfection, it is necessary to understand the limits of dopant incorporation and the behavior of the impurity in the material. In this study, N-type doping above 10 19 cm -3 has been achieved in InP and InGaAs using Sn as a dopant. P-type Zn doping at these levels has also been achieved in these materials but p type activation above ∼3 x 10 18 cm -3 in InP has not been seen. All materials were grown by the metalorganic chemical vapor deposition (MOCVD) crystal growth technique. Effective diffusion coefficients have been measured for Zn and Sn in both materials from analysis of secondary ion mass spectra (SIMS) of specially grown and annealed samples

Direct Current Sputter Epitaxy of Heavily Doped p+ Layer for Monocrystalline Si Solar Cells

Directory of Open Access Journals (Sweden)

Wenchang Yeh

2017-01-01

Full Text Available Sputter epitaxy of p+ layer for fabrication of Si solar cells (SCs was demonstrated. Hall carrier concentration of p+ layer was 2.6 × 1020 cm−3 owing to cosputtering of B with Si at low temperature, which had enabled heavy and shallow p+ dope layer. p+nn+ SCs were fabricated and influence of p+ and n+ layers was investigated. Internal quantum efficiency (IQE of p+nn+ SCs was 95% at visible light and was larger than 60% at ultraviolet (UV light when the p+ layer was thinner than 30 nm. At near infrared (NIR, extra increment on IQE was achieved by rear n+ back surface field (BSF layer with a thickness thinner than 100 nm.

Effect of 60Co γ-irradiation on the nature of electronic transport in heavily doped n-type GaN based Schottky photodetectors

Science.gov (United States)

Chatterjee, Abhishek; Khamari, Shailesh K.; Porwal, S.; Kher, S.; Sharma, T. K.

2018-04-01

GaN Schottky photodetectors are fabricated on heavily doped n-type GaN epitaxial layers grown by the hydride vapour phase epitaxy technique. The effect of 60Co γ-radiation on the electronic transport in GaN epilayers and Schottky detectors is studied. In contrast to earlier observations, a steady rise in the carrier concentration with increasing irradiation dose is clearly seen. By considering a two layer model, the contribution of interfacial dislocations in carrier transport is isolated from that of the bulk layer for both the pristine and irradiated samples. The bulk carrier concentration is fitted by using the charge balance equation which indicates that no new electrically active defects are generated by γ-radiation even at 500 kGy dose. The irradiation induced rise in the bulk carrier concentration is attributed to the activation of native Si impurities that are already present in an electrically inert form in the pristine sample. Further, the rise in interfacial contribution in the carrier concentration is governed by the enhanced rate of formation of nitrogen vacancies by irradiation, which leads to a larger diffusion of oxygen impurities. A large value of the characteristic tunnelling energy for both the pristine and irradiated Au/Ni/GaN Schottky devices confirms that the dislocation-assisted tunnelling dominates the low temperature current transport even after irradiation. The advantage of higher displacement energy and larger bandgap of GaN as compared to GaAs is evident from the change in leakage current after irradiation. Further, a fast recovery of the photoresponse of GaN photodetectors after irradiation signifies their compatibility to operate in high radiation zones. The results presented here are found to be crucial in understanding the interaction of 60Co γ-irradiation with n+-GaN epilayers.

Effects of Ba doping on physical properties of La-Ca-Mn-O thin films

CERN Document Server

Hong, N H; Sakai, J; Iwasaki, H

2003-01-01

Transport and magnetic properties of La-Ba-Ca-Mn-O thin films fabricated by the pulsed laser deposition technique had been investigated systematically to see the effects of substitution of the small atom Ca by Ba which is much bigger. The induced insulator-to-metal (IM) transition was obtained not only in compositions near 0.5 and 0.18 which are boundaries between metallic and insulating phases but also in the heavily doped region. In the region of x > 0.5, the Ba doping causes an anomalous response of the system to the magnetic field and a positive magnetoresistance was observed. Besides, our results concerning the vicinity of 0.5 imply the existence of phase separation. As for x < 0.5, the doping enhances remarkably the paramagnetism-ferromagnetism transition and the IM transition temperatures.

Stability and diffusion of interstitital and substitutional Mn in GaAs of different doping types

CERN Document Server

Pereira, LMC; Decoster, S; Correia, JG; Amorim, LM; da Silva, MR; Araújo, JP; Vantomme, A

2012-01-01

We report on the lattice location of Mn impurities (< 0.05%) in undoped (semi-insulating) and heavily $n$-type doped GaAs, by means of $\\beta^{-}$-emission channeling from the decay of $^{56}$Mn produced at ISOLDE/CERN. In addition to the majority substituting for Ga, we locate up to 30% of the Mn impurites on tetrahedral interstitial sites with As nearest neighbors. In line with the recently reported high thermal stability of interstitial Mn in heavily $p$-type doped GaAs [L. M. C. Pereira et al., Appl. Phys. Lett. 98, 201905 (2011)], the interstitial fraction is found to be stable up to 400$^{\\circ}$C, with an activation energy for diffusion of 1.7–2.3 eV. By varying the concentration of potentially trapping defects, without a measurable effect on the migration energy of the interstitial impurities, we conclude that the observed high thermal stability is characteristic of isolated interstitial Mn. Being difficult to reconcile with the general belief that interstitial Mn is the donor defect that out-dif...

Lifetime studies of self-activated photoluminescence in heavily silicon-doped GaAs

Science.gov (United States)

Sauncy, T.; Palsule, C. P.; Holtz, M.; Gangopadhyay, S.; Massie, S.

1996-01-01

We report results of a detailed temperature dependence study of photoluminescence lifetime and continuous emission properties in silicon-doped GaAs. The primary focus is on a defect-related emission at 1.269 eV (T=20 K). GaAs crystals were grown using molecular-beam epitaxy with most of the experiments conducted on a sample having a carrier concentration of 4.9×1018 cm-3. The intensity is seen to decrease above 100 K, with no corresponding decrease in the measured lifetime of 9.63+/-0.25 ns. The intensity decrease implies an activation energy of 19+/-2 meV, which is approximately one order of magnitude smaller than what was previously obtained for similar defects in Czochralski-grown GaAs with other dopants. We interpret our results in terms of a configuration coordinate model and obtain a more complete picture of the energy-level structure. The experiments indicate that the upper level in the recombination process is about 20 meV below the conduction-band continuum, with the lower state approximately 300 meV above the valence band. Our results are consistent with the identification of the corresponding defect complex microstructure as being a silicon-at-gallium substitution, weakly interacting with a gallium vacancy second-nearest neighbor, known as the Si-Y defect complex.

Evaluation of local free carrier concentrations in individual heavily-doped GaN:Si micro-rods by micro-Raman spectroscopy

Science.gov (United States)

Mohajerani, M. S.; Khachadorian, S.; Schimpke, T.; Nenstiel, C.; Hartmann, J.; Ledig, J.; Avramescu, A.; Strassburg, M.; Hoffmann, A.; Waag, A.

2016-02-01

Three-dimensional III-nitride micro-structures are being developed as a promising candidate for the future opto-electrical devices. In this study, we demonstrate a quick and straight-forward method to locally evaluate free-carrier concentrations and a crystalline quality in individual GaN:Si micro-rods. By employing micro-Raman mapping and analyzing lower frequency branch of A1(LO)- and E1(LO)-phonon-plasmon-coupled modes (LPP-), the free carrier concentrations are determined in axial and planar configurations, respectively. Due to a gradual doping profile along the micro-rods, a highly spatially resolved mapping on the sidewall is exploited to reconstruct free carrier concentration profile along the GaN:Si micro-rods. Despite remarkably high free carrier concentrations above 1 × 1020 cm-3, the micro-rods reveal an excellent crystalline quality, without a doping-induced stress.

Impurity incorporation in R.A.D. polysilicon layers and consequences on their electrical properties

International Nuclear Information System (INIS)

Revel, G.; Deschamps, N.; Deville, J.P.; Texier-Hervo, C.; Belouet, C.

1982-01-01

The growth of polysilicon layers by direct freezing of a film on a carbon ribbon by the RAD process goes along with a contamination of the silicon melt by carbon and its compositional impurities. This paper reports on this contamination effect studied mainly by means of neutron activation analyses (NAA) and its consequences on the electrical properties of the layers. The purification of the carbon ribbons in chlorine at high temperatures results in low contamination levels of the melt; NAA evidenced a significant segregation at the growth front, the effective partition coefficients determined being in the 10 - 1 to 10 - 3 range. Even though impurities are shown to impair the device performances, it is concluded that they are not necessarily incorporated in an electrically active form. Finally, AM 1 conversion efficiencies of 12% are reported for RAD cells 4 cm 2 in size. (Auth.)

Superconductivity and low temperature electrical transport in B-doped CVD nanocrystalline diamond

Directory of Open Access Journals (Sweden)

Milos Nesladek, Jiri J. Mares, Dominique Tromson, Christine Mer, Philippe Bergonzo, Pavel Hubik and Jozef Kristofik

2006-01-01

Full Text Available In this work, we report on superconductivity (SC found in thin B-doped nanocrystalline diamond films, prepared by the PE-CVD technique. The thickness of the films varies from about 100 to 400 nm, the films are grown on low-alkaline glass at substrate temperatures of about 500–700 °C. The SIMS measurements show that films can be heavily doped with boron in concentrations in the range of 3×1021 cm−3. The Raman spectra show Fano resonances, confirming the substitutional B-incorporation. The low temperature magnetotransport measurements reveal a positive magnetoresistance. The SC transition is observed at about Tc=1.66 K. A simple theory exploiting the concept of weak localization accounting for this transition is proposed.

Ion-implanted capacitively coupled silicon strip detectors with integrated polysilicon bias resistors processed on a 100 mm wafer

International Nuclear Information System (INIS)

Hietanen, I.; Lindgren, J.; Orava, R.; Tuuva, T.; Voutilainen, M.; Brenner, R.; Andersson, M.; Leinonen, K.; Ronkainen, H.

1991-01-01

Double-sided silicon strip detectors with integrated coupling capacitors and polysilicon resistors have been processed on a 100 mm wafer. A detector with an active area of 19x19 mm 2 was connected to LSI readout electronics and tested. The strip pitch of the detector is 25 μm on the p-side and 50 μm on the n-side. The readout pitch is 50 μm on both sides. The number of readout strips is 774 and the total number of strips is 1161. On the p-side a signal-to-noise of 35 has been measured using a 90 Sr β-source. The n-side has been studied using a laser. (orig.)

EBSD analysis of polysilicon films formed by aluminium induced crystallization of amorphous silicon

Energy Technology Data Exchange (ETDEWEB)

Tuezuen, O. [InESS, UMR 7163 CNRS-ULP, 23 rue du Loess, F-67037 Strasbourg Cedex 2 (France)], E-mail: Ozge.Tuzun@iness.c-strasbourg.fr; Auger, J.M. [InESS, UMR 7163 CNRS-ULP, 23 rue du Loess, F-67037 Strasbourg Cedex 2 (France); SMS Centre, UMR CNRS 5146, Ecole des Mines de Saint Etienne, 158 Cours Fauriel, 42023 Saint Etienne Cedex 2 (France); Gordon, I. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Focsa, A.; Montgomery, P.C. [InESS, UMR 7163 CNRS-ULP, 23 rue du Loess, F-67037 Strasbourg Cedex 2 (France); Maurice, C. [SMS Centre, UMR CNRS 5146, Ecole des Mines de Saint Etienne, 158 Cours Fauriel, 42023 Saint Etienne Cedex 2 (France); Slaoui, A. [InESS, UMR 7163 CNRS-ULP, 23 rue du Loess, F-67037 Strasbourg Cedex 2 (France); Beaucarne, G.; Poortmans, J. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium)

2008-08-30

Among the methods for enlarging the grain size of polycrystalline silicon (poly-Si) thin films, aluminium induced crystallization (AIC) of amorphous silicon is considered to be a very promising approach. In the AIC process, a thin a-Si layer on top of an aluminium layer crystallizes at temperatures well below the eutectic temperature of the Al/Si system (T{sub eu} = 577 deg. C). By means of electron backscattering diffraction (EBSD), we have mainly studied the effect of the aluminium layer quality varying the deposition system on the grain size, the defects and the preferential crystallographic orientation. We have found a strong correlation between the mean grain size and the size distribution with the Al deposition system and the surface quality. Furthermore, we show for the first time that more than 50% of the surface of the AIC films grown on alumina substrates are (103) preferentially oriented, instead of the commonly observed (100) preferential orientation. This may have important consequences for epitaxial thickening of the AIC layer into polysilicon absorber layers for solar cells.

Further considerations for damping in heavily insulated pipe systems

International Nuclear Information System (INIS)

Anderson, M.J.; Lindquist, M.R.; Severud, L.K.

1985-01-01

Over the past several years a body of test data has been accumulated which demonstrates that damping in small diameter heavily insulated pipe systems is much larger than presently recommended by Regulatory Guide 1.61. This data is generally based on pipe systems using a stand-off insulation design with a heater annulus. Additional tests have how been completed on similar pipe systems using a strap-on insulation design without the heater annulus. Results indicate some reduction in damping over the stand-off designs. Test data has also been obtained on a larger sixteen-inch diameter heavily insulated pipe system. Results of these two additional test series are presented. Revised damping values for seismic design of heavily insulated pipe systems are then recommended

Further considerations for damping in heavily insulated pipe systems

International Nuclear Information System (INIS)

Anderson, M.J.; Lindquist, M.R.; Severud, L.K.

1985-01-01

Over the past several years a body of test data has been accumulated which demonstrates that damping in small diameter heavily insulated pipe systems is much larger than presently recommended by Regulatory Code 1.61. This data is generally based on pipe systems using a stand-off insulation design with a heater annulus. Additional tests have now been completed on similar pipe systems using a strap-on insulation design without the heater annulus. Results indicate some reduction in damping over the stand-off designs. Test data has also been obtained on a larger sixteen-inch diameter heavily insulated pipe system. Results of these two additional test series are presented. Revised damping values for seismic design for heavily insulated pipe systems are then recommended

Heavily Graphitic-Nitrogen Self-doped High-porosity Carbon for the Electrocatalysis of Oxygen Reduction Reaction

Science.gov (United States)

Feng, Tong; Liao, Wenli; Li, Zhongbin; Sun, Lingtao; Shi, Dongping; Guo, Chaozhong; Huang, Yu; Wang, Yi; Cheng, Jing; Li, Yanrong; Diao, Qizhi

2017-11-01

Large-scale production of active and stable porous carbon catalysts for oxygen reduction reaction (ORR) from protein-rich biomass became a hot topic in fuel cell technology. Here, we report a facile strategy for synthesis of nitrogen-doped porous nanocarbons by means of a simple two-step pyrolysis process combined with the activation of zinc chloride and acid-treatment process, in which kidney bean via low-temperature carbonization was preferentially adopted as the only carbon-nitrogen sources. The results show that this carbon material exhibits excellent ORR electrocatalytic activity, and higher durability and methanol-tolerant property compared to the state-of-the-art Pt/C catalyst for the ORR, which can be mainly attributed to high graphitic-nitrogen content, high specific surface area, and porous characteristics. Our results can encourage the synthesis of high-performance carbon-based ORR electrocatalysts derived from widely-existed natural biomass.

Reconceptualising the Gender of Fitness Doping: Performing and Negotiating Masculinity through Drug-Use Practices

Directory of Open Access Journals (Sweden)

Jesper Andreasson

2015-08-01

Full Text Available This article analyses self-portrayals and gender constructions among Swedish male bodybuilders who are engaged in fitness doping. The empirical material comes from a larger ethnographic investigation into gym culture. The results show that there is a strong propensity to conform with particular gender fantasies that rests heavily on a binary understanding of gendered, doped bodies. However, this storyline does not apprehend the entire self-presentation of the analysed drug users. Negotiations and inclusive subversions of traditional gender norms are also expressed. For example, the narratives show how the use of performance-enhancing substances makes it possible for (heterosexual men to approach, touch and express feelings of desire towards other men and their bodies. As such, this practice can be viewed as a contestation of hegemonic gender values, in which masculinity and fitness doping are detached from a quite heterosexist understanding, and turned into a symbolic world of homoerotic pleasure.

Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires.

Science.gov (United States)

Song, Erdong; Li, Qiming; Swartzentruber, Brian; Pan, Wei; Wang, George T; Martinez, Julio A

2016-01-08

The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. Selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.

Excitonic optical bistability in n-type doped semiconductors

International Nuclear Information System (INIS)

Nguyen Ba An; Le Thi Cat Tuong

1991-07-01

A resonant monochromatic pump laser generates coherent excitons in an n-type doped semiconductor. Both exciton-exciton and exciton-donor interactions come into play. The former interaction can give rise to the appearance of optical bistability which is heavily influenced by the latter one. When optical bistability occurs at a fixed laser frequency both its holding intensity and hysteresis loop size are shown to decrease with increasing donor concentration. Two possibilities are suggested for experimentally determining one of the two parameters of the system - the exciton-donor coupling constant and the donor concentration, if the other parameter is known beforehand. (author). 36 refs, 2 figs

Design, Simulation and Characteristics Research of the Interface Circuit based on nano-polysilicon thin films pressure sensor

Science.gov (United States)

Zhao, Xiaosong; Zhao, Xiaofeng; Yin, Liang

2018-03-01

This paper presents a interface circuit for nano-polysilicon thin films pressure sensor. The interface circuit includes consist of instrument amplifier and Analog-to-Digital converter (ADC). The instrumentation amplifier with a high common mode rejection ratio (CMRR) is implemented by three stages current feedback structure. At the same time, in order to satisfy the high precision requirements of pressure sensor measure system, the 1/f noise corner of 26.5 mHz can be achieved through chopping technology at a noise density of 38.2 nV/sqrt(Hz).Ripple introduced by chopping technology adopt continuous ripple reduce circuit (RRL), which achieves the output ripple level is lower than noise. The ADC achieves 16 bits significant digit by adopting sigma-delta modulator with fourth-order single-bit structure and digital decimation filter, and finally achieves high precision integrated pressure sensor interface circuit.

Design analysis of doped-silicon surface plasmon resonance immunosensors in mid-infrared range.

Science.gov (United States)

DiPippo, William; Lee, Bong Jae; Park, Keunhan

2010-08-30

This paper reports the design analysis of a microfabricatable mid-infrared (mid-IR) surface plasmon resonance (SPR) sensor platform. The proposed platform has periodic heavily doped profiles implanted into intrinsic silicon and a thin gold layer deposited on top, making a physically flat grating SPR coupler. A rigorous coupled-wave analysis was conducted to prove the design feasibility, characterize the sensor's performance, and determine geometric parameters of the heavily doped profiles. Finite element analysis (FEA) was also employed to compute the electromagnetic field distributions at the plasmon resonance. Obtained results reveal that the proposed structure can excite the SPR on the normal incidence of mid-IR light, resulting in a large probing depth that will facilitate the study of larger analytes. Furthermore, the whole structure can be microfabricated with well-established batch protocols, providing tunability in the SPR excitation wavelength for specific biosensing needs with a low manufacturing cost. When the SPR sensor is to be used in a Fourier-transform infrared (FTIR) spectroscopy platform, its detection sensitivity and limit of detection are estimated to be 3022 nm/RIU and ~70 pg/mm(2), respectively, at a sample layer thickness of 100 nm. The design analysis performed in the present study will allow the fabrication of a tunable, disposable mid-IR SPR sensor that combines advantages of conventional prism and metallic grating SPR sensors.

Optimization of process parameter variations on leakage current in in silicon-oninsulator vertical double gate mosfet device

Directory of Open Access Journals (Sweden)

K.E. Kaharudin

2015-12-01

Full Text Available This paper presents a study of optimizing input process parameters on leakage current (IOFF in silicon-on-insulator (SOI Vertical Double-Gate,Metal Oxide Field-Effect-Transistor (MOSFET by using L36 Taguchi method. The performance of SOI Vertical DG-MOSFET device is evaluated in terms of its lowest leakage current (IOFF value. An orthogonal array, main effects, signal-to-noise ratio (SNR and analysis of variance (ANOVA are utilized in order to analyze the effect of input process parameter variation on leakage current (IOFF. Based on the results, the minimum leakage current ((IOFF of SOI Vertical DG-MOSFET is observed to be 0.009 nA/µm or 9 ρA/µm while keeping the drive current (ION value at 434 µA/µm. Both the drive current (ION and leakage current (IOFF values yield a higher ION/IOFF ratio (48.22 x 106 for low power consumption application. Meanwhile, polysilicon doping tilt angle and polysilicon doping energy are recognized as the most dominant factors with each of the contributing factor effects percentage of 59% and 25%.

Resonant Raman and FTIR spectra of carbon doped GaN

Science.gov (United States)

Ito, S.; Kobayashi, H.; Araki, K.; Suzuki, K.; Sawaki, N.; Yamashita, K.; Honda, Y.; Amano, H.

2015-03-01

Intentionally carbon (C) doped (0 0 0 1)GaN was grown using C2H2 on a sapphire substrate by metalorganic vapor phase epitaxy. Optical spectra of the heavily doped samples were investigated at room temperature. In Raman spectra excited by the 325 nm line of a He-Cd laser, multiple LO phonon scattering signals up to 7th order were observed, and the A1(LO) phonon energy was determined to be 737.5 cm-1 (91.45 meV). In infrared reflectance spectra, on the other hand, a local vibration mode was found at 777.5 cm-1, which is attributed to a Ga-C bond in the GaN matrix suggesting that the C sits on an N site (CN). In spite of the strong suggestion of CN, the samples did not show p-type conduction. Possible origin of the carrier compensation is discussed in relation to the enhancement of defect related yellow luminescence in the photoluminescence spectra.

Stark shift of impurity doped quantum dots: Role of noise

Science.gov (United States)

Arif, Sk. Md.; Bera, Aindrila; Ghosh, Anuja; Ghosh, Manas

2018-02-01

Present study makes a punctilious investigation of the profiles of Stark shift (SS) of doped GaAs quantum dot (QD) under the supervision of Gaussian white noise. A few physical parameters have been varied and the consequent variations in the SS profiles have been monitored. The said physical parameters comprise of magnetic field, confinement potential, dopant location, dopant potential, noise strength, aluminium concentration (only for AlxGa1-x As alloy QD), position-dependent effective mass (PDEM), position-dependent dielectric screening function (PDDSF), anisotropy, hydrostatic pressure (HP) and temperature. The SS profiles unfurl interesting features that heavily depend upon the particular physical quantity concerned, presence/absence of noise and the manner (additive/multiplicative) noise enters the system. The study highlights feasible means of maximizing SS of doped QD in presence of noise by suitable adjustment of several control parameters. The study deems importance in view of technological applications of QD devices where noise plays some prominent role.

Low p-type contact resistance by field-emission tunneling in highly Mg-doped GaN

Science.gov (United States)

Okumura, Hironori; Martin, Denis; Grandjean, Nicolas

2016-12-01

Mg-doped GaN with a net acceptor concentration (NA-ND) in the high 1019 cm-3 range was grown using ammonia molecular-beam epitaxy. Electrical properties of NiO contact on this heavily doped p-type GaN were investigated. A potential-barrier height of 0.24 eV was extracted from the relationship between NA-ND and the specific contact resistivity (ρc). We found that there is an optimum NA-ND value of 5 × 1019 cm-3 for which ρc is as low as 2 × 10-5 Ω cm2. This low ρc is ascribed to hole tunneling through the potential barrier at the NiO/p+-GaN interface, which is well accounted for by the field-emission model.

Strong coupling between bi-dimensional electron gas and nitrogen localized states in heavily doped GaAs1-xN x structures

International Nuclear Information System (INIS)

Hamdouni, A.; Bousbih, F.; Ben Bouzid, S.; Oueslati, M.; Chtourou, R.; Harmand, J.C.

2005-01-01

We report a low-temperature photoluminescence spectra (LTPL) of GaAs 1-x N x layers and two-dimension electron gas (2DEG) GaAs 1-x N x /AlGaAs modulation doped heterostructure grown on GaAs substrates by molecular beam epitaxy (MBE) with low nitrogen content [N] = 2 x 10 18 cm -3 . At low temperature, PL spectra of GaAs 1-x N x layers are governed by several features associate to the excitons bound to nitrogen complexes, these features disappear in (2DEG) GaAs 1-x N x /AlGaAs modulation doped heterostructure and the PL peak energy decrease with the laser power excitation. This effect is explained by the strongly coupling of the (2DEG) fundamental state with the nitrogen localized states. An activated energy of about 55 meV is deduced by photoluminescence measurements in the 10-300 K range for a laser power excitation P = 6 W/cm 2

Exploring the doping effects of Ag in p-type PbSe compounds with enhanced thermoelectric performance

Science.gov (United States)

Wang, Shanyu; Zheng, Gang; Luo, Tingting; She, Xiaoyu; Li, Han; Tang, Xinfeng

2011-11-01

In this study, we prepared a series of Ag-doped PbSe bulk materials by a melting-quenching process combined with a subsequent spark plasma sintering process, and systematically investigated the doping effects of Ag on the thermoelectric properties. Ag substitution in the Pb site does not introduce resonant levels near the valence band edge or detectable change in the density of state in the vicinity of the Fermi level, but moves the Fermi level down and increases the carrier concentration to a maximum value of ~4.7 × 1019 cm-3 which is still insufficient for heavily doped PbSe compounds. Nonetheless, the non-monotonic variation in carrier concentration with increasing Ag content indicates that Ag doping reaches the solution limit at ~1.0% and the excessive Ag presumably acts as donors in the materials. Moreover, the large energy gap of the PbSe-based material wipes off significant 'roll-over' in the Seebeck coefficient at elevated temperatures which gives rise to high power factors, being comparable to p-type Te analogues. Consequently, the maximum ZT reaches ~1.0 for the 1.5% Ag-doped samples with optimized carrier density, which is ~70% improvement in comparison with an undoped sample and also superior to the commercialized p-type PbTe materials.

Ion-channeling analysis of As relocation in heavily doped Si:As irradiated with high-energy ions

International Nuclear Information System (INIS)

Lulli, G.; Albertazzi, E.; Bianconi, M.; Ferri, M.

2003-01-01

Silicon on insulator layers doped with 8x10 20 As cm -3 and thermally equilibrated at 1100 deg. C, have been irradiated with 2 MeV Si + ions. Rutherford backscattering-channeling analysis shows an increase in As disorder upon irradiation significantly larger than the increase in Si disorder, while electrical measurements show a large decrease in electrical activation. Monte Carlo simulation of channeling angular scans suggests that the enhanced As disorder effect is due to the preferential relocation of dopant atoms slightly displaced from lattice sites, which appear the main reason responsible for the electrical deactivation in the unirradiated sample and are believed to be in the form of As-vacancy clusters. Upon 600 deg. C 15 s annealing, the As atoms randomly relocated by ion irradiation almost completely recover their original configuration, probably capturing vacancies and forming, again, the complexes dissociated by ion irradiation

Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires

International Nuclear Information System (INIS)

Song, Erdong; Martinez, Julio A; Li, Qiming; Pan, Wei; Wang, George T; Swartzentruber, Brian

2016-01-01

The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. Selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power. (paper)

Thermal, dielectric studies on pure and amino acid ( L-glutamic acid, L-histidine, L-valine) doped KDP single crystals

Science.gov (United States)

Kumaresan, P.; Moorthy Babu, S.; Anbarasan, P. M.

2008-05-01

Amino acids ( L-glutamic acid, L-histidine, L-valine) doped potassium dihydrogen phospate crystals are grown by solution growth technique. Slow cooling as well as slow evaporation methods were employed to grow these crystals. The concentration of dopants in the mother solution was varied from 0.1 mol% to 10 mol%. The solubility data for all dopants concentration were determined. There is variation in pH value and hence, there is habit modification of the grown crystals were characterized with UV-VIS, FT-IR studies, SHG trace elements and dielectric studies reveal slight distortion of lattice parameter for the heavily doped KDP crystals. UV-Visible spectra confirm the improvement in the transparency of these crystals on doping metal ions. FT-IR spectra reveal strong absorption band between 1400 and 1600 cm -1 for metal ion doped crystals. TGA-DTA studies reveal good thermal stability. The dopants increase the hardness value of the material and it also depends on the concentration of the dopants. Amino acids doping improved the NLO properties. The detailed results on the spectral parameters, habit modifications and constant values will be presented.

Porous boron doped diamonds as metal-free catalysts for the oxygen reduction reaction in alkaline solution

Science.gov (United States)

Suo, Ni; Huang, Hao; Wu, Aimin; Cao, Guozhong; Hou, Xiaoduo; Zhang, Guifeng

2018-05-01

Porous boron doped diamonds (BDDs) were obtained on foam nickel substrates with a porosity of 80%, 85%, 90% and 95% respectively by hot filament chemical vapor deposition (HFCVD) technology. Scanning electron microscopy (SEM) reveals that uniform and compact BDDs with a cauliflower-like morphology have covered the overall frame of the foam nickel substrates. Raman spectroscopy shows that the BDDs have a poor crystallinity due to heavily doping boron. X-ray photoelectron spectroscopy (XPS) analysis effectively demonstrates that boron atoms can be successfully incorporated into the crystal lattice of diamonds. Electrochemical measurements indicate that the oxygen reduction potential is unaffected by the specific surface area (SSA), and both the onset potential and the limiting diffusion current density are enhanced with increasing SSA. It is also found that the durability and methanol tolerance of the boron doped diamond catalysts are attenuated as the increasing of SSA. The SSA of the catalyst is directly proportional to the oxygen reduction activity and inversely to the durability and methanol resistance. These results provide a reference to the application of porous boron doped diamonds as potential cathodic catalysts for the oxygen reduction reaction in alkaline solution by adjusting the SSA.

High-beam quality, high-efficiency laser based on fiber with heavily Yb(3+)-doped phosphate core and silica cladding.

Science.gov (United States)

Egorova, O N; Semjonov, S L; Medvedkov, O I; Astapovich, M S; Okhrimchuk, A G; Galagan, B I; Denker, B I; Sverchkov, S E; Dianov, E M

2015-08-15

We have fabricated and tested a composite fiber with an Yb(3+)-doped phosphate glass core and silica cladding. Oscillation with a slope efficiency of 74% was achieved using core pumping at 976 nm with fiber lengths of 48-90 mm in a simple laser configuration, where the cavity was formed by a high-reflectivity Bragg grating and the cleaved fiber end. The measured M(2) factors were as low as 1.05-1.22 even though the fiber was multimode at the lasing wavelength.

Stratigraphy of a diamond epitaxial three-dimensional overgrowth using doping superlattices

Science.gov (United States)

Lloret, F.; Fiori, A.; Araujo, D.; Eon, D.; Villar, M. P.; Bustarret, E.

2016-05-01

The selective doped overgrowth of 3D mesa patterns and trenches has become an essential fabrication step of advanced monolithic diamond-based power devices. The methodology here proposed combines the overgrowth of plasma-etched cylindrical mesa structures with the sequential growth of doping superlattices. The latter involve thin heavily boron doped epilayers separating thicker undoped epilayers in a periodic fashion. Besides the classical shape analysis under the scanning electron microscope relying on the appearance of facets corresponding to the main crystallographic directions and their evolution toward slow growing facets, the doping superlattices were used as markers in oriented cross-sectional lamellas prepared by focused ion beam and observed by transmission electron microscopy. This stratigraphic approach is shown here to be applicable to overgrown structures where faceting was not detectable. Intermediate growth directions were detected at different times of the growth process and the periodicity of the superlattice allowed to calculate the growth rates and parameters, providing an original insight into the planarization mechanism. Different configurations of the growth front were obtained for different sample orientations, illustrating the anisotropy of the 3D growth. Dislocations were also observed along the lateral growth fronts with two types of Burger vector: b 01 1 ¯ = /1 2 [ 01 1 ¯ ] and b 112 = /1 6 [ 112 ] . Moreover, the clustering of these extended defects in specific regions of the overgrowth prompted a proposal of two different dislocation generation mechanisms.

Improvement in the performance of graphene nanoribbon p-i-n tunneling field effect transistors by applying lightly doped profile on drain region

Science.gov (United States)

Naderi, Ali

2017-12-01

In this paper, an efficient structure with lightly doped drain region is proposed for p-i-n graphene nanoribbon field effect transistors (LD-PIN-GNRFET). Self-consistent solution of Poisson and Schrödinger equation within Nonequilibrium Green’s function (NEGF) formalism has been employed to simulate the quantum transport of the devices. In proposed structure, source region is doped by constant doping density, channel is an intrinsic GNR, and drain region contains two parts with lightly and heavily doped doping distributions. The important challenge in tunneling devices is obtaining higher current ratio. Our simulations demonstrate that LD-PIN-GNRFET is a steep slope device which not only reduces the leakage current and current ratio but also enhances delay, power delay product, and cutoff frequency in comparison with conventional PIN GNRFETs with uniform distribution of impurity and with linear doping profile in drain region. Also, the device is able to operate in higher drain-source voltages due to the effectively reduced electric field at drain side. Briefly, the proposed structure can be considered as a more reliable device for low standby-power logic applications operating at higher voltages and upper cutoff frequencies.

High Capacity of Hard Carbon Anode in Na-Ion Batteries Unlocked by PO _x Doping

Energy Technology Data Exchange (ETDEWEB)

Li, Zhifei; Ma, Lu; Surta, Todd Wesley; Bommier, Clement; Jian, Zelang; Xing, Zhenyu; Stickle, William F.; Dolgos, Michelle; Amine, Khalil; Lu, Jun; Wu, Tianpin; Ji, Xiulei

2016-08-12

The capacity of hard carbon anodes in Na-ion batteries 2.5 rarely reaches values beyond 300 mAh/g. We report that doping POx into local structures of hard carbon increases its reversible capacity from 283 to 359 mAh/g. We confirm that the doped POx is redox inactive by X-ray adsorption near edge structure measurements, thus not contributing to the higher capacity. We observe two significant changes of hard carbon's local structures caused by doping. First, the (002) d-spacing inside the turbostratic nanodomains is increased, revealed by both laboratory and synchrotron X-ray diffraction. Second, doping turns turbostratic nanodomains more defective along ab planes, indicated by neutron total scattering and the associated pair distribution function studies. The local structural changes of hard carbon are correlated to the higher capacity, where both the plateau and slope regions in the potential profiles are enhanced. Our study demonstrates that Na-ion storage in hard carbon heavily depends on carbon local structures, where such structures, despite being disordered, can be tuned toward unusually high capacities.

Explosive phenomena in heavily irradiated NaCl

NARCIS (Netherlands)

denHartog, HW; Vainshtein, DI; Matthews, GE; Williams, RT

1997-01-01

In heavily irradiated NaCl crystals explosive phenomena can be initiated during irradiation or afterwards when samples are heated to temperatures between 100 and 250 degrees C. During irradiation of NaCl Na and Cl-2 precipitates and void structures are produced along with the accumulation of stored

Exploring the doping effects of Ag in p-type PbSe compounds with enhanced thermoelectric performance

International Nuclear Information System (INIS)

Wang Shanyu; Zheng Gang; Luo Tingting; She Xiaoyu; Li Han; Tang Xinfeng

2011-01-01

In this study, we prepared a series of Ag-doped PbSe bulk materials by a melting-quenching process combined with a subsequent spark plasma sintering process, and systematically investigated the doping effects of Ag on the thermoelectric properties. Ag substitution in the Pb site does not introduce resonant levels near the valence band edge or detectable change in the density of state in the vicinity of the Fermi level, but moves the Fermi level down and increases the carrier concentration to a maximum value of ∼4.7 × 10 19 cm -3 which is still insufficient for heavily doped PbSe compounds. Nonetheless, the non-monotonic variation in carrier concentration with increasing Ag content indicates that Ag doping reaches the solution limit at ∼1.0% and the excessive Ag presumably acts as donors in the materials. Moreover, the large energy gap of the PbSe-based material wipes off significant 'roll-over' in the Seebeck coefficient at elevated temperatures which gives rise to high power factors, being comparable to p-type Te analogues. Consequently, the maximum ZT reaches ∼1.0 for the 1.5% Ag-doped samples with optimized carrier density, which is ∼70% improvement in comparison with an undoped sample and also superior to the commercialized p-type PbTe materials.

Low-frequency noise behavior of polysilicon emitter bipolar junction transistors: a review

Science.gov (United States)

Deen, M. Jamal; Pascal, Fabien

2003-05-01

For many analog integrated circuit applications, the polysilicon emitter bipolar junction transistor (PE-BJT) is still the preferred choice because of its higher operational frequency and lower noise performance characteristics compared to MOS transistors of similar active areas and at similar biasing currents. In this paper, we begin by motivating the reader with reasons why bipolar transistors are still of great interest for analog integrated circuits. This motivation includes a comparison between BJT and the MOSFET using a simple small-signal equivalent circuit to derive important parameters that can be used to compare these two technologies. An extensive review of the popular theories used to explain low frequency noise results is presented. However, in almost all instances, these theories have not been fully tested. The effects of different processing technologies and conditions on the noise performance of PE-BJTs is reviewed and a summary of some of the key technological steps and device parameters and their effects on noise is discussed. The effects of temperature and emitter geometries scaling is reviewed. It is shown that dispersion of the low frequency noise in ultra-small geometries is a serious issue since the rate of increase of the noise dispersion is faster than the noise itself as the emitter geometry is scaled to smaller values. Finally, some ideas for future research on PE-BJTs, some of which are also applicable to SiGe heteorjunction bipolar transistors and MOSFETs, are presented after the conclusions.

Development of efficient, radiation-insensitive GaAs:Zn LEDs

International Nuclear Information System (INIS)

Barnes, C.E.

1977-01-01

Although amphoterically Si doped GaAs LEDs are commercially popular because of their high light output, they are extremely sensitive to irradiation. Therefore, it would be desirable to have a viable alternative available for radiation environment applications. In this work it is shown that by increasing the hole concentration in the active region of nonamphoterically doped GaAs LEDs, one can simultaneously achieve high light output and low radiation sensitivity. Experimental results indicate that the minority carrier lifetime is smaller in more heavily doped devices so that the lifetime-damage constant, tau/sub o/K, is also smaller. Hence, the heavily doped devices should have greater radiation hardness. Neutron-induced light output degradation data as a function of hole concentration confirm this conclusion. The results also show that the pre-irradiation light output is greatest in the heavily doped LEDs. The accompanying decrease of tau/sub o/ in the heavily doped devices indicates that the total minority carrier lifetime is at least partially controlled by the radiative lifetime; a requirement for simultaneously achieving radiation hardness and high initial light output. Finally, an experimental comparison with amphoterically Si doped LEDs shows that the heavily doped devices are superior for neutron fluences greater than 2 x 10 12 n/cm 2

Back wall solar cell

Science.gov (United States)

Brandhorst, H. W., Jr. (Inventor)

1978-01-01

A solar cell is disclosed which comprises a first semiconductor material of one conductivity type with one face having the same conductivity type but more heavily doped to form a field region arranged to receive the radiant energy to be converted to electrical energy, and a layer of a second semiconductor material, preferably highly doped, of opposite conductivity type on the first semiconductor material adjacent the first semiconductor material at an interface remote from the heavily doped field region. Instead of the opposite conductivity layer, a metallic Schottky diode layer may be used, in which case no additional back contact is needed. A contact such as a gridded contact, previous to the radiant energy may be applied to the heavily doped field region of the more heavily doped, same conductivity material for its contact.

Heavily doped M1−xUxF2+2x fluorites studied by quasielastic neutron scattering(M=Ba) and specific heat measurements (M=Pb)

DEFF Research Database (Denmark)

Andersen, Niels Hessel; Clausen, Kurt Nørgaard; Kjems, Jørgen

1983-01-01

of doping is an increase of the thermally generated defect concentration; at high temperatures the effect is reversed. The microscopic defect structure of Ba0.9U0.1F2.2 has been studied by diffuse quasielastic neutron scattering experiments at room temperature. The experimental observations are in good......The thermal generation of defects in pure and doped Pb1−xUxF2+2x (x=0, 0.05and0.10) has been studied by specific heat measurements between 475 k and 875 k. A simple phenomenological mean field thermodynamic model has been developed and used to interpret the data. At low temperatures the result...

Thermal, Dielectric Studies on Pure and Amino Acid L-Glutamic Acid, L-Histidine L-Valine Doped Potassium Dihydrogen Phosphate Single Crystals

Science.gov (United States)

Kumaresan, P.; Babu, S. Moorthy; Anbarasan, P. M.

Amino acids (L-Glutamic acid, L-Histidine, L-Valine) doped potassium dihydrogen phosphate crystals were grown by the solution growth technique. Slow cooling as well as slow evaporation methods were employed to grow these crystals. The concentration of dopants in the mother solution was varied from 0.1 mole % to 10 mole %. The solubility data for all dopant concentrations were determined. The variation in pH and the corresponding habit modification of the grown crystals were characterized with UV - VIS, FT-IR and SHG trace elements, and dielectric studies reveal slight distortion of lattice parameter for the heavily doped KDP crystals. TGA-DTA studies reveal good thermal stability. The dopants increase the hardness value of the material, which also depends on the concentration of the dopants. Amino acids doping improved the NLO properties. The detailed results on the spectral parameters, habit modifications and constant values will be presented.

Dual-gate polysilicon nanoribbon biosensors enable high sensitivity detection of proteins

International Nuclear Information System (INIS)

Zeimpekis, I; Sun, K; Hu, C; Ditshego, N M J; De Planque, M R R; Chong, H M H; Morgan, H; Ashburn, P; Thomas, O

2016-01-01

We demonstrate the advantages of dual-gate polysilicon nanoribbon biosensors with a comprehensive evaluation of different measurement schemes for pH and protein sensing. In particular, we compare the detection of voltage and current changes when top- and bottom-gate bias is applied. Measurements of pH show that a large voltage shift of 491 mV pH"−"1 is obtained in the subthreshold region when the top-gate is kept at a fixed potential and the bottom-gate is varied (voltage sweep). This is an improvement of 16 times over the 30 mV pH"−"1 measured using a top-gate sweep with the bottom-gate at a fixed potential. A similar large voltage shift of 175 mV is obtained when the protein avidin is sensed using a bottom-gate sweep. This is an improvement of 20 times compared with the 8.8 mV achieved from a top-gate sweep. Current measurements using bottom-gate sweeps do not deliver the same signal amplification as when using bottom-gate sweeps to measure voltage shifts. Thus, for detecting a small signal change on protein binding, it is advantageous to employ a double-gate transistor and to measure a voltage shift using a bottom-gate sweep. For top-gate sweeps, the use of a dual-gate transistor enables the current sensitivity to be enhanced by applying a negative bias to the bottom-gate to reduce the carrier concentration in the nanoribbon. For pH measurements, the current sensitivity increases from 65% to 149% and for avidin sensing it increases from 1.4% to 2.5%. (paper)

Watermelon-like iron nanoparticles: Cr doping effect on magnetism and magnetization interaction reversal

Energy Technology Data Exchange (ETDEWEB)

Kaur, Maninder; Dai, Qilin; Bowden, Mark E.; Engelhard, Mark H.; Wu, Yaqiao; Tang, Jinke; Qiang, You

2013-06-26

Chromium (Cr) forms a solid solution with iron (Fe) lattice when doped in core-shell iron -iron oxide nanocluster (NC) and shows a mixed phase of sigma (σ) FeCr and bcc Fe. The Cr dopant affects heavily the magnetization and magnetic reversal process, and causes the hysteresis loop to shrink near the zero field axis. Dramatic transformation happens from dipolar interaction (0 at. % Cr) to strong exchange interaction (8 at. % of Cr) is confirmed from the Henkel plot and delta M plot, and is explained by a water-melon model of core-shell NC system.

Erbium-doped phosphate glass waveguide on silicon with 4.1 dB/cm gain at 1.535 µm

Science.gov (United States)

Yan, Y. C.; Faber, A. J.; de Waal, H.; Kik, P. G.; Polman, A.

1997-11-01

Erbium-doped multicomponent phosphate glass waveguides were deposited by rf sputtering techniques. The Er concentration was 5.3×1020cm-3. By pumping the waveguide at 980 nm with a power of ˜21 mW, a net optical gain of 4.1 dB at 1.535 μm was achieved. This high gain per unit length at low pump power could be achieved because the Er-Er cooperative upconversion interactions in this heavily Er-doped phosphate glass are very weak [the upconversion coefficient is (2.0±0.5)×10-18 cm3/s], presumably due to the homogeneous distribution of Er in the glass and due to the high optical mode confinement in the waveguide which leads to high pump power density at low pump power.

Antimony segregation in Ge and formation of n-type selectively doped Ge films in molecular beam epitaxy

Energy Technology Data Exchange (ETDEWEB)

Yurasov, D. V., E-mail: Inquisitor@ipm.sci-nnov.ru; Antonov, A. V.; Drozdov, M. N.; Schmagin, V. B.; Novikov, A. V. [Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, 603950 Nizhny Novgorod (Russian Federation); Lobachevsky State University of Nizhni Novgorod, 23 Prospekt Gagarina, 603950 Nizhny Novgorod (Russian Federation); Spirin, K. E. [Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, 603950 Nizhny Novgorod (Russian Federation)

2015-10-14

Antimony segregation in Ge(001) films grown by molecular beam epitaxy was studied. A quantitative dependence of the Sb segregation ratio in Ge on growth temperature was revealed experimentally and modeled theoretically taking into account both the terrace-mediated and step-edge-mediated segregation mechanisms. A nearly 5-orders-of-magnitude increase in the Sb segregation ratio in a relatively small temperature range of 180–350 °C was obtained, which allowed to form Ge:Sb doped layers with abrupt boundaries and high crystalline quality using the temperature switching method that was proposed earlier for Si-based structures. This technique was employed for fabrication of different kinds of n-type Ge structures which can be useful for practical applications like heavily doped n{sup +}-Ge films or δ-doped layers. Estimation of the doping profiles sharpness yielded the values of 2–5 nm per decade for the concentration gradient at the leading edge and 2–3 nm for the full-width-half-maximum of the Ge:Sb δ-layers. Electrical characterization of grown Ge:Sb structures revealed nearly full electrical activation of Sb atoms and the two-dimensional nature of charge carrier transport in δ-layers.

High reliability EPI-base radiation hardened power transistor

International Nuclear Information System (INIS)

Clark, L.E.; Saltich, J.L.

1978-01-01

A high-voltage power transistor is described which is able to withstand fluences as high as 3 x 10 14 neutrons per square centimeter and still be able to operate satisfactorily. The collector may be made essentially half as thick and twice as heavily doped as normally and its base is made in two regions which together are essentially four times as thick as the normal power transistor base region. The base region has a heavily doped upper region and a lower region intermediate the upper heavily doped region and the collector. The doping in the intermediate region is as close to intrinsic as possible, in any event less than about 3 x 10 15 impurities per cubic centimeter. The second base region has small width in comparison to the first base region, the ratio of the first to the second being at least about 5 to 1. The base region having the upper heavily doped region and the intermediate or lower low doped region contributes to the higher breakdown voltage which the transistor is able to withstand. The high doping of the collector region essentially lowers that portion of the breakdown voltage achieved by the collector region. Accordingly, it is necessary to transfer certain of this breakdown capability to the base region and this is achieved by using the upper region of heavily doped and an intermediate or lower region of low doping

Electronic and physico-chemical properties of nanometric boron delta-doped diamond structures

International Nuclear Information System (INIS)

Chicot, G.; Fiori, A.; Tran Thi, T. N.; Bousquet, J.; Delahaye, J.; Grenet, T.; Eon, D.; Omnès, F.; Bustarret, E.; Volpe, P. N.; Tranchant, N.; Mer-Calfati, C.; Arnault, J. C.; Gerbedoen, J. C.; Soltani, A.; De Jaeger, J. C.; Alegre, M. P.; Piñero, J. C.; Araújo, D.; Jomard, F.

2014-01-01

Heavily boron doped diamond epilayers with thicknesses ranging from 40 to less than 2 nm and buried between nominally undoped thicker layers have been grown in two different reactors. Two types of [100]-oriented single crystal diamond substrates were used after being characterized by X-ray white beam topography. The chemical composition and thickness of these so-called delta-doped structures have been studied by secondary ion mass spectrometry, transmission electron microscopy, and spectroscopic ellipsometry. Temperature-dependent Hall effect and four probe resistivity measurements have been performed on mesa-patterned Hall bars. The temperature dependence of the hole sheet carrier density and mobility has been investigated over a broad temperature range (6 K  2 /Vs, independently of the layer thickness and the substrate type. Comparison with previously published data and theoretical calculations showed that scattering by ionized impurities explained only partially this low common value. None of the delta-layers showed any sign of confinement-induced mobility enhancement, even for thicknesses lower than 2 nm

Microstructure evolution and phase transition in La/Mn doped barium titanate ceramics

Directory of Open Access Journals (Sweden)

Vesna Paunović

2010-12-01

Full Text Available La/Mn codoped BaTiO3 with different La2O3 content, ranging from 0.1 to 5.0 at% La, was investigated regarding their microstructural and dielectric characteristics. The content of 0.05 at% Mn was constant in all investigated samples. The samples were sintered at 1320°C and 1350°C for two hours. Microstructural studies were done using SEM and EDS analysis. The fine-grained microstructure was obtained even for low content of La. The appearance of secondary abnormal grains with serrated features along grain boundaries was observed in 1.0 at% La-BaTiO3 sintered at 1350°C. Nearly flat permittivity-temperature response was obtained in specimens with 2.0 and 5.0 at% La. Using the modified Curie-Weiss law a critical exponent γ and C’were calculated. The obtained values of γ pointed out the diffuse phase transformation in heavily doped BaTiO3 and great departure from the Curie-Weiss law for low doped ceramics.

Operation of heavily irradiated silicon detectors in non-depletion mode

International Nuclear Information System (INIS)

Verbitskaya, E.; Eremin, V.; Ilyashenko, I.; Li, Z.; Haerkoenen, J.; Tuovinen, E.; Luukka, P.

2006-01-01

The non-depletion detector operation mode has generally been disregarded as an option in high-energy physics experiments. In this paper, the non-depletion operation is examined by detailed analysis of the electric field distribution and the current pulse response of heavily irradiated silicon (Si) detectors. The previously reported model of double junction in heavily irradiated Si detector is further developed and a simulation of the current pulse response has been performed. It is shown that detectors can operate in a non-depletion mode due to the fact that the value of the electric field in a non-depleted region is high enough for efficient carrier drift. This electric field originates from the current flow through the detector and a consequent drop of the potential across high-resistivity bulk of a non-depleted region. It is anticipated that the electric field in a non-depleted region, which is still electrically neutral, increases with fluence that improves the non-depleted detector operation. Consideration of the electric field in a non-depleted region allows the explanation of the recorded double-peak current pulse shape of heavily irradiated Si detectors and definition of the requirements for the detector operational conditions. Detailed reconstruction of the electric field distribution gives new information on radiation effects in Si detectors

Galvanomagnetic properties and electronic structure of iron-doped PbTe

Energy Technology Data Exchange (ETDEWEB)

Skipetrov, E. P., E-mail: skip@mig.phys.msu.ru [Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Faculty of Materials Science, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Kruleveckaya, O. V.; Skipetrova, L. A. [Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Knotko, A. V. [Faculty of Materials Science, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Faculty of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Slynko, E. I.; Slynko, V. E. [Institute of Materials Science Problems, National Academy of Sciences of Ukraine, Chernivtsy 58001 (Ukraine)

2015-11-21

We synthesize an iron-doped PbTe single-crystal ingot and investigate the phase composition and distribution of the iron impurity along the ingot as well as galvanomagnetic properties in weak magnetic fields (4.2 K ≤ T ≤ 300 K, B ≤ 0.07 T) of Pb{sub 1−y}Fe{sub y}Te alloys. We find microscopic inclusions enriched with iron and regions with a chemical composition close to FeTe in the heavily doped samples, while the iron impurity content in the main phase rises only slightly along the length of the ingot reaching the impurity solubility limit at approximately 0.6 mol. %. Samples from the initial and the middle parts of the ingot are characterized by p-type metal conductivity. An increase of the iron impurity content leads to a decrease in the free hole concentration and to a stabilization of galvanomagnetic parameters due to the pinning of the Fermi level by the iron resonant impurity level E{sub Fe} lying under the bottom of the valence band (E{sub v} − E{sub Fe} ≈ 16 meV). In the samples from the end of the ingot, a p-n inversion of the conductivity type and an increase of the free electron concentration along the ingot are revealed despite the impurity solubility limit being reached. The kinetics of changes of charge carrier concentration and of the Fermi energy along the ingot is analyzed in the framework of the six-band Dimmock dispersion relation. A model is proposed for the electronic structure rearrangement of Pb{sub 1−y}Fe{sub y}Te with doping, which may also be used for PbTe doped with other transition metals.

Nanodiamonds for device applications: An investigation of the properties of boron-doped detonation nanodiamonds.

Science.gov (United States)

Afandi, Abdulkareem; Howkins, Ashley; Boyd, Ian W; Jackman, Richard B

2018-02-19

The inclusion of boron within nanodiamonds to create semiconducting properties would create a new class of applications in the field of nanodiamond electronics. Theoretical studies have differed in their conclusions as to whether nm-scale NDs would support a stable substitutional boron state, or whether such a state would be unstable, with boron instead aggregating or attaching to edge structures. In the present study detonation-derived NDs with purposefully added boron during the detonation process have been studied with a wide range of experimental techniques. The DNDs are of ~4 nm in size, and have been studied with CL, PL, Raman and IR spectroscopies, AFM and HR-TEM and electrically measured with impedance spectroscopy; it is apparent that the B-DNDs studied here do indeed support substitutional boron species and hence will be acting as semiconducting diamond nanoparticles. Evidence for moderate doping levels in some particles (~10 17 B cm -3 ), is found alongside the observation that some particles are heavily doped (~10 20 B cm -3 ) and likely to be quasi-metallic in character. The current study has therefore shown that substitutional boron doping in nm NDs is in fact possible, opening-up the path to a whole host of new applications for this interesting class of nano-particles.

Heavy Mg-doping of (Al,Ga)N films for potential applications in deep ultraviolet light-emitting structures

Science.gov (United States)

Liang, Y. H.; Towe, E.

2018-03-01

Doping of high aluminum-containing (Al,Ga)N thin films has remained a challenging problem that has hindered progress in the development of deep ultraviolet light-emitters. This paper reports on the synthesis and use of heavily doped (Al,Ga)N films in deep ultraviolet (˜274 nm) light-emitting structures; these structures were synthesized by molecular beam epitaxy under liquid-metal growth conditions that facilitate the incorporation of extremely high density of Mg dopant impurities (up to 5 × 1019 cm-3) into aluminum-rich (Al,Ga)N thin films. Prototypical light-emitting diode structures incorporating Al0.7Ga0.3N films doped with Mg impurities that ionize to give free hole carrier concentrations of up to 6 × 1017 cm-3 exhibit external quantum efficiencies of up 0.56%; this is an improvement from previous devices made from molecular beam epitaxy-grown materials. This improvement is believed to be due to the high hole carrier concentration enabled by the relatively low activation energy of 220 meV compared to the expected values of 408-507 meV for Al0.7Ga0.3N films.

Quantum Mechanical Modeling of Ballistic MOSFETs

Science.gov (United States)

Svizhenko, Alexei; Anantram, M. P.; Govindan, T. R.; Biegel, Bryan (Technical Monitor)

2001-01-01

The objective of this project was to develop theory, approximations, and computer code to model quasi 1D structures such as nanotubes, DNA, and MOSFETs: (1) Nanotubes: Influence of defects on ballistic transport, electro-mechanical properties, and metal-nanotube coupling; (2) DNA: Model electron transfer (biochemistry) and transport experiments, and sequence dependence of conductance; and (3) MOSFETs: 2D doping profiles, polysilicon depletion, source to drain and gate tunneling, understand ballistic limit.

Computer assisted design of poly-silicon gated enhancement-mode, lateral double quantum dot devices for quantum computing

Science.gov (United States)

Bishop, Nathaniel; Young, Ralph; Borras Pinilla, Carlos; Stalford, Harold; Nielsen, Erik; Muller, Richard; Rahman, Rajib; Tracy, Lisa; Wendt, Joel; Lilly, Michael; Carroll, Malcolm

2012-02-01

We discuss trade-offs of different double quantum dot and charge sensor lay-outs using computer assisted design (CAD). We use primarily a semi-classical model, augmented with a self-consistent configuration interaction method. Although CAD for quantum dots is difficult due to uncontrolled factors (e.g., disorder), different ideal designs can still be compared. Comparisons of simulation and measured dot characteristics, such as capacitance, show that CAD can agree well with experiment for relevant cases. CAD results comparing several different designs will be discussed including a comparison to measurement results from the same designs. Trade-offs between poly-silicon and metal gate lay-outs will also be discussed. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. The work was supported by the Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Remote Excavation of Heavily Contaminated UXO Sites. The Range Master

National Research Council Canada - National Science Library

Crandall, Alan L

2007-01-01

USA Environmental, Inc., and Timberline Environmental Services, Inc., developed the Range Master, a remote controlled scraper with an integrated power screen, to excavate and sift the top 12 inches of heavily contaminated UXO sites...

Electrochemical Decontamination of Painted and Heavily Corroded Metals

International Nuclear Information System (INIS)

Marczak, S.; Anderson, J.; Dziewinski, J.

1998-01-01

The radioactive metal wastes that are generated from nuclear fuel plants and radiochemical laboratories are mainly contaminated by the surface deposition of radioactive isotopes. There are presently several techniques used in removing surface contamination involving physical and chemical processes. However, there has been very little research done in the area of soiled, heavily oxidized, and painted metals. Researchers at Los Alamos National Laboratory have been developing electrochemical procedures for the decontamination of bare and painted metal objects. These methods have been found to be effective on highly corroded as well as relatively new metals. This study has been successful in decontaminating projectiles and shrapnel excavated during environmental restoration projects after 40+ years of exposure to the elements. Heavily corroded augers used in sampling activities throughout the area were also successfully decontaminated. This process has demonstrated its effectiveness and offers several advantages over the present metal decontamination practices of media blasting and chemical solvents. These advantages include the addition of no toxic or hazardous chemicals, low operating temperature and pressure, and easily scaleable equipment. It is in their future plans to use this process in the decontamination of gloveboxes destined for disposal as TRU waste

Characteristics of Polysilicon Wire Glucose Sensors with a Surface Modified by Silica Nanoparticles/γ-APTES Nanocomposite

Directory of Open Access Journals (Sweden)

Jheng-Jia Jhuang

2011-03-01

Full Text Available This report investigates the sensing characteristics of polysilicon wire (PSW glucose biosensors, including thickness characteristics and line-width effects on detection limits, linear range and interference immunity with membranes coated by micropipette/spin-coating and focus-ion-beam (FIB processed capillary atomic-force-microscopy (C-AFM tip scan/coating methods. The PSW surface was modified with a mixture of 3-aminopropyl-triethoxysilane (γ-APTES and polydimethylsiloxane (PDMS-treated hydrophobic fumed silica nanoparticles (NPs. We found that the thickness of the γ-APTES+NPs nonocomposite could be controlled well at about 22 nm with small relative standard deviation (RSD with repeated C-AFM tip scan/coatings. The detection limit increased and linear range decreased with the line width of the PSW through the tip-coating process. Interestingly, the interference immunity ability improves as the line width increases. For a 500 nm-wide PSW, the percentage changes of the channel current density changes (ΔJ caused by acetaminophen (AP can be kept below 3.5% at an ultra-high AP-to-glucose concentration ratio of 600:1. Simulation results showed that the line width dependence of interference immunity was strongly correlated with the channel electrical field of the PSW biosensor.

Ultramicroporous carbon with extremely narrow pore distribution and very high nitrogen doping for efficient methane mixture gases upgrading

KAUST Repository

Yao, Kexin

2017-06-24

It is notably challenging to fabricate heavily heteroatom-doped porous carbonaceous materials with narrow ultramicropore size distributions for highly effective mixed-gas separation. In this study, new carbon-based materials with narrow ultramicropore size (<7 Å) distributions (>95%) and high N doping contents (>10 at%) are fabricated through the pyrolysis of a perchloro-substituted porous covalent triazine-based framework (ClCTF). In particular, the sample prepared at 650 °C (ClCTF-1-650) possesses the highest ultramicropores content (98%) and large N content (12 at%) and demonstrates a very high CH and CO capacity, as well as a low N uptake under ambient conditions. The extraordinarily high CH/N and CO/N selectivities correlate with both the ideal adsorption solution theory (IAST) method and performed dynamic separation experiments (breakthrough experiments). The results reported in this study far exceed the CH/N and CO/N selectivities of previously reported carbon-based adsorbents including various nitrogen-doped ones. These results are believed to be associated with the unusually high N content, as well as the suitably narrow ultramicropore size distribution. This report introduces a new pathway to design porous absorbents with precisely controlled ultramicropores for gas separation.

To dope or not to dope

DEFF Research Database (Denmark)

Overbye, Marie Birch; Knudsen, Mette Lykke; Pfister, Gertrud Ursula

2013-01-01

tAim: This study aims to examine the circumstances which athletes say affect their (hypothetical) consid-erations of whether to dope or not and explore the differences between athletes of different gender, ageand sport type.Methods: 645 elite athletes (mean age: 22.12; response rate: 43%) represe......tAim: This study aims to examine the circumstances which athletes say affect their (hypothetical) consid-erations of whether to dope or not and explore the differences between athletes of different gender, ageand sport type.Methods: 645 elite athletes (mean age: 22.12; response rate: 43......%) representing 40 sports completed aweb-based questionnaire. Participants were asked to imagine themselves in a situation in which theyhad to decide whether to dope or not to dope and then evaluate how different circumstances would affecttheir decisions.Results: Multiple circumstances had an effect on athletes......’ hypothetical decisions. The most effective deter-rents were related to legal and social sanctions, side-effects and moral considerations. Female athletesand younger athletes evaluated more reasons as deterrents than older, male athletes. When confrontedwith incentives to dope, the type of sport was often...

The challenge of screen printed Ag metallization on nano-scale poly-silicon passivated contacts for silicon solar cells

Science.gov (United States)

Jiang, Lin; Song, Lixin; Yan, Li; Becht, Gregory; Zhang, Yi; Hoerteis, Matthias

2017-08-01

Passivated contacts can be used to reduce metal-induced recombination for higher energy conversion efficiency for silicon solar cells, and are obtained increasing attentions by PV industries in recent years. The reported thicknesses of passivated contact layers are mostly within tens of nanometer range, and the corresponding metallization methods are realized mainly by plating/evaporation technology. This high cost metallization cannot compete with the screen printing technology, and may affect its market potential comparing with the presently dominant solar cell technology. Very few works have been reported on screen printing metallization on passivated contact solar cells. Hence, there is a rising demand to realize screen printing metallization technology on this topic. In this work, we investigate applying screen printing metallization pastes on poly-silicon passivated contacts. The critical challenge for us is to build low contact resistance that can be competitive to standard technology while restricting the paste penetrations within the thin nano-scale passivated contact layers. The contact resistivity of 1.1mohm-cm2 and the open circuit voltages > 660mV are achieved, and the most appropriate thickness range is estimated to be around 80 150nm.

Influence of rare-earth additives (La, Sm and Dy on the microstructure and dielectric properties of doped BaTiO3 ceramics

Directory of Open Access Journals (Sweden)

Paunović Vesna

2010-01-01

Full Text Available A series of La/Mn, Sm/Mn and Dy/Mn codoped BaTiO3 samples were prepared by the conventional solid state procedure with dopant concentrations ranging from 0.1 up to 2.0 at%. The specimens were sintered at 1320°C and 1350°C in an air atmosphere for two hours. The low doped samples demonstrated a mainly uniform and homogeneous microstructure with average grain sizes ranging from 0.3 μm to 5.0 μm. The appearance of secondary abnormal grains in the fine grain matrix and core-shell structure were observed in highly doped La/BaTiO3 and Dy/BaTiO3 sintered at 1350°C. The low doped samples, sintered at 1350°C, display a high value of dielectric permittivity at room temperature, 6800 for Sm/BaTiO3, 5900 for Dy/BaTiO3 and 3100 for La/BaTiO3. A nearly flat permittivity-response was obtained in specimens with 2.0 at% additive content. Using a modified Curie-Weiss law the Curie-like constant C⁄ and a critical exponent γ were calculated. The obtained values of γ pointed out the diffuse phase transformation in heavily doped BaTiO3 samples.

Two-band analysis of hole mobility and Hall factor for heavily carbon-doped p-type GaAs

Science.gov (United States)

Kim, B. W.; Majerfeld, A.

1996-02-01

We solve a pair of Boltzmann transport equations based on an interacting two-isotropic-band model in a general way first to get transport parameters corresponding to the relaxation time. We present a simple method to calculate effective relaxation times, separately for each band, which compensate for the inherent deficiencies in using the relaxation time concept for polar optical-phonon scattering. Formulas for calculating momentum relaxation times in the two-band model are presented for all the major scattering mechanisms of p-type GaAs for simple, practical mobility calculations. In the newly proposed theoretical framework, first-principles calculations for the Hall mobility and Hall factor of p-type GaAs at room temperature are carried out with no adjustable parameters in order to obtain direct comparisons between the theory and recently available experimental results. In the calculations, the light-hole-band nonparabolicity is taken into account on the average by the use of energy-dependent effective mass obtained from the kṡp method and valence-band anisotropy is taken partly into account by the use the Wiley's overlap function.. The calculated Hall mobilities show a good agreement with our experimental data for carbon-doped p-GaAs samples in the range of degenerate hole densities. The calculated Hall factors show rH=1.25-1.75 over hole densities of 2×1017-1×1020 cm-3.

The Anti-Doping Movement.

Science.gov (United States)

Willick, Stuart E; Miller, Geoffrey D; Eichner, Daniel

2016-03-01

Historical reports of doping in sports date as far back as the ancient Greek Olympic Games. The anti-doping community considers doping in sports to be cheating and a violation of the spirit of sport. During the past century, there has been an increasing awareness of the extent of doping in sports and the health risks of doping. In response, the anti-doping movement has endeavored to educate athletes and others about the health risks of doping and promote a level playing field. Doping control is now undertaken in most countries around the world and at most elite sports competitions. As athletes have found new ways to dope, however, the anti-doping community has endeavored to strengthen its educational and deterrence efforts. It is incumbent upon sports medicine professionals to understand the health risks of doping and all doping control processes. Copyright © 2016 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Doped Organic Transistors.

Science.gov (United States)

Lüssem, Björn; Keum, Chang-Min; Kasemann, Daniel; Naab, Ben; Bao, Zhenan; Leo, Karl

2016-11-23

Organic field-effect transistors hold the promise of enabling low-cost and flexible electronics. Following its success in organic optoelectronics, the organic doping technology is also used increasingly in organic field-effect transistors. Doping not only increases device performance, but it also provides a way to fine-control the transistor behavior, to develop new transistor concepts, and even improve the stability of organic transistors. This Review summarizes the latest progress made in the understanding of the doping technology and its application to organic transistors. It presents the most successful doping models and an overview of the wide variety of materials used as dopants. Further, the influence of doping on charge transport in the most relevant polycrystalline organic semiconductors is reviewed, and a concise overview on the influence of doping on transistor behavior and performance is given. In particular, recent progress in the understanding of contact doping and channel doping is summarized.

Positron trapping in heavily irradiated semiconductors

International Nuclear Information System (INIS)

Moser, P.; Pautrat, J.L.; Corbel, C.; Hautojarvi, P.

1985-01-01

Vacancy processes are studied in several heavily irradiated semiconductors. Specimens are ZnTe, CdTe, CdTe (In), InP, InP (Cr), InP (Zn) and Ge. Irradiations are made at 20 K using a 3 MeV Van de Graaff electron accelerator. Doses are 4 x 10 18 e - /cm 2 . Lifetime measurements are made at 77 K at each step of an isochronal annealing (30 min 20 K). In each specimen, the results show a significant increase of the lifetime (+ 30 at + 50 ps) which anneals out in different steps restoring the initial lifetime. The steps are sharp (ΔT/T=0.3) with the exception of InP, InP(Cr), InP(Zn), (ΔT/T=0.9). Tentative interpretations are given

Implicit versus explicit attitude to doping: Which better predicts athletes' vigilance towards unintentional doping?

Science.gov (United States)

Chan, Derwin King Chung; Keatley, David A; Tang, Tracy C W; Dimmock, James A; Hagger, Martin S

2018-03-01

This preliminary study examined whether implicit doping attitude, explicit doping attitude, or both, predicted athletes' vigilance towards unintentional doping. A cross-sectional correlational design. Australian athletes (N=143;M age =18.13, SD=4.63) completed measures of implicit doping attitude (brief single-category implicit association test), explicit doping attitude (Performance Enhancement Attitude Scale), avoidance of unintentional doping (Self-Reported Treatment Adherence Scale), and behavioural vigilance task of unintentional doping (reading the ingredients of an unfamiliar food product). Positive implicit doping attitude and explicit doping attitude were negatively related to athletes' likelihood of reading the ingredients table of an unfamiliar food product, and positively related to athletes' vigilance towards unintentional doping. Neither attitude measures predicted avoidance of unintentional doping. Overall, the magnitude of associations by implicit doping attitude appeared to be stronger than that of explicit doping attitude. Athletes with positive implicit and explicit doping attitudes were less likely to read the ingredients table of an unknown food product, but were more likely to be aware of the possible presence of banned substances in a certain food product. Implicit doping attitude appeared to explain athletes' behavioural response to the avoidance of unintentional doping beyond variance explained by explicit doping attitude. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Doping profile measurements in silicon using terahertz time domain spectroscopy (THz-TDS) via electrochemical anodic oxidation

Science.gov (United States)

Tulsyan, Gaurav

Doping profiles are engineered to manipulate device properties and to determine electrical performances of microelectronic devices frequently. To support engineering studies afterward, essential information is usually required from physically characterized doping profiles. Secondary Ion Mass Spectrometry (SIMS), Spreading Resistance Profiling (SRP) and Electrochemical Capacitance Voltage (ECV) profiling are standard techniques for now to map profile. SIMS yields a chemical doping profile via ion sputtering process and owns a better resolution, whereas ECV and SRP produce an electrical doping profile detecting free carriers in microelectronic devices. The major difference between electrical and chemical doping profiles is at heavily doped regions greater than 1020 atoms/cm3. At the profile region over the solubility limit, inactive dopants induce a flat plateau and detected by electrical measurements only. Destructive techniques are usually designed as stand-alone systems to study impurities. For an in-situ process control purpose, non-contact methods, such as ellipsometry and non-contact capacitance voltage (CV) techniques are current under development. In this theses work, terahertz time domain spectroscopy (THz-TDS) is utilized to achieve electrical doping profile in both destructive and non-contact manners. In recent years the Terahertz group at Rochester Institute Technology developed several techniques that use terahertz pulses to non-destructively map doping profiles. In this thesis, we study a destructive but potentially higher resolution version of the terahertz based approach to map the profile of activated dopants and augment the non-destructive approaches already developed. The basic idea of the profile mapping approach developed in this MS thesis is to anodize, and thus oxidize to silicon dioxide, thin layers (down to below 10 nm) of the wafer with the doping profile to be mapped. Since the dopants atoms and any free carriers in the silicon oxide thin

Current Status of Doping in Japan Based on Japan Anti-Doping Disciplinary Panels of the Japan Anti-Doping Agency (JADA): A Suggestion on Anti-Doping Activities by Pharmacists in Japan.

Science.gov (United States)

Imanishi, Takashi; Kawabata, Takayoshi; Takayama, Akira

2017-01-01

In 2009, the Japan Anti-Doping Agency (JADA) established the "Sports Pharmacist Accreditation Program" to prevent doping in sports. Since then, anti-doping activities in Japan have been attracting attention. In this study, we investigated research about the current status of doping from 2007 to 2014 in Japan to make anti-doping activities more concrete, and we also discussed future anti-doping activities by pharmacists. In Japan, bodybuilding was the sporting event with the highest number and rate of doping from 2007 to 2014. Many of the positive doping cases were detected for class S1 (anabolic agents), S5 (diuretics and masking agents), and S6 (stimulants). Within class S1, supplements were the main cause of positive doping. Within class S5, medicines prescribed by medical doctors were the main cause of positive doping. Within class S6, non-prescription medicines (e.g., OTC) were the main cause of positive doping. When we looked at the global statistics on doping, many of the positive doping cases were detected for class S1. On comparing the Japanese statistics with the global statistics, the rate of positive doping caused by class S1 was significantly lower, but that caused by classes S5 and S6 was significantly higher in Japan than in the world. In conclusion, pharmacists in Japan should pay attention to class S1, S5, and S6 prohibited substances and to the sport events of bodybuilding. Based on this study, sports pharmacists as well as common pharmacists should suggest new anti-doping activities to prevent doping in the future.

Wet chemical treatment of boron doped emitters on n-type (1 0 0) c-Si prior to amorphous silicon passivation

Energy Technology Data Exchange (ETDEWEB)

Meddeb, H., E-mail: hosny.meddeb@gmail.com [KACST-Intel Consortium Center of Excellence in Nano-manufacturing Applications (CENA), Riyadh (Saudi Arabia); IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Research and Technology Center of Energy, Photovoltaic Department, Borj-Cedria Science and Technology Park, BP 95, 2050 (Tunisia); University of Carthage, Faculty of Sciences of Bizerta (Tunisia); Bearda, T.; Recaman Payo, M.; Abdelwahab, I. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Abdulraheem, Y. [Electrical Engineering Department, College of Engineering & Petroleum, Kuwait University, P.O. Box 5969, 13060 Safat (Kuwait); Ezzaouia, H. [Research and Technology Center of Energy, Photovoltaic Department, Borj-Cedria Science and Technology Park, BP 95, 2050 (Tunisia); Gordon, I.; Szlufcik, J. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Poortmans, J. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Department of Electrical Engineering (ESAT), K.U. Leuven, 3001 Leuven (Belgium); Faculty of Sciences, University of Hasselt, Martelarenlaan 42, 3500 Hasselt (Belgium)

2015-02-15

Highlights: • The influence of the cleaning process using different HF-based cleaning on the amorphous silicon passivation of homojunction boron doped emitters is analyzed. • The effect of boron doping level on surface characteristics after wet chemical cleaning: For heavily doped surfaces, the reduction in contact angle was less pronounced, which proves that such surfaces are more resistant to oxide formation and remain hydrophobic for a longer time. In the case of low HF concentration, XPS measurements show higher oxygen concentrations for samples with higher doping level, probably due to the incomplete removal of the native oxide. • Higher effective lifetime is achieved at lower doping for all considered different chemical pre-treatments. • A post-deposition annealing improves the passivation level yielding emitter saturation currents determined by Auger recombination in the order of 70 fA/cm{sup 2} and below. • The dominance of Auger recombination over other type of B-induced defects on lifetime quality in the case of our p+ emitter. - Abstract: The influence of the cleaning process on the amorphous silicon passivation of homojunction emitters is investigated. A significant variation in the passivation quality following different cleaning sequences is not observed, even though differences in cleaning performance are evident. These results point out the effectiveness of our cleaning treatment and provide a hydrogen termination for intrinsic amorphous silicon passivation. A post-deposition treatment improves the passivation level yielding emitter saturation currents determined by Auger recombination in the order of 70 fA/cm{sup 2} and below.

Addition of sunitinib to cetuximab and irinotecan in patients with heavily pre-treated advanced colorectal cancer

DEFF Research Database (Denmark)

Qvortrup, Camilla; Jensen, Benny Vittrup; Jørgensen, Trine Lembrecht

2010-01-01

Results of continuous sunitinib, in combination with cetuximab and irinotecan every other week (SIC) for compassionate use in heavily pre-treated patients with mCRC are presented.......Results of continuous sunitinib, in combination with cetuximab and irinotecan every other week (SIC) for compassionate use in heavily pre-treated patients with mCRC are presented....

Cu-Doped-CdS/In-Doped-CdS Cosensitized Quantum Dot Solar Cells

Directory of Open Access Journals (Sweden)

Lin Li

2014-01-01

Full Text Available Cu-doped-CdS and In-doped-CdS cosensitized (Cu-doped-CdS/In-doped-CdS quantum dot solar cells (QDSCs are introduced here. Different cosensitized sequences, doping ratios, and the thickness (SILAR cycles of Cu-doped-CdS and In-doped-CdS are discussed. Compared with undoped CdS QDSCs, the short circuit current density, UV-Vis absorption spectra, IPCE (monochromatic incident photon-to-electron conversion, open circuit voltage, and so on are all improved. The photoelectric conversion efficiency has obviously improved from 0.71% to 1.28%.

Electrical characterization of single cells using polysilicon wire ion sensor in an isolation window.

Science.gov (United States)

Wu, You-Lin; Hsu, Po-Yen; Hsu, Chung-Ping; Wang, Chih-Cheng; Lee, Li-Wen; Lin, Jing-Jenn

2011-10-01

A polysilicon wire (PSW) sensor can detect the H(+) ion density (pH value) of the medium coated on its surface, and different cells produce different extracellular acidification and hence different H(+) ion densities. Based on this, we used a PSW sensor in combination with a mold-cast polydimethylsiloxane (PDMS) isolation window to detect the adhesion, apoptosis and extracellular acidification of single normal cells and single cancer cells. Single living human normal cells WI38, MRC5, and BEAS-2B as well as non-small-cell lung cancer (NSCLC) cells A549, H1299, and CH27 were cultivated separately inside the isolation window. The current flowing through the PSW channel was measured. From the PSW channel current change as a function of time, we determined the cell adhesion time by observing the time required for the current change to saturate, since a stable extracellular ion density was established after the cells were completely adhered to the PSW surface. The apoptosis of cells can also be determined when the channel current change drops to zero. We found that all the NSCLC cells had a higher channel current change and hence a lower pH value than the normal cells anytime after they were seeded. The corresponding average pH values were 5.86 for A549, 6.00 for H1299, 6.20 for CH27, 6.90 for BEAS-2B, 6.96for MRC5, and 7.02 for WI38, respectively, after the cells were completely adhered to the PSW surface. Our results show that NSCLC cells have a stronger cell-substrate adhesion and a higher extracellular acidification rate than normal cells.

Highly concentrated, stable nitrogen-doped graphene for supercapacitors: Simultaneous doping and reduction

Energy Technology Data Exchange (ETDEWEB)

Jiang Baojiang [College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin (China); Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People' s Republic of China, Heilongjiang University, Harbin (China); Tian Chungui; Wang Lei; Sun Li; Chen Chen; Nong Xiaozhen [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People' s Republic of China, Heilongjiang University, Harbin (China); Qiao Yingjie, E-mail: qiaoyingjie@hrbeu.edu.cn [College of Materials Science and Chemical Engineering, Harbin Engineering University, Harbin (China); Fu Honggang, E-mail: fuhg@vip.sina.com [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People' s Republic of China, Heilongjiang University, Harbin (China)

2012-02-01

In this work, we developed a concentrated ammonia-assisted hydrothermal method to obtain N-doped graphene sheets by simultaneous N-doping and reduction of graphene oxide (GO) sheets. The effects of hydrothermal temperature on the surface chemistry and the structure of N-doped graphene sheets were also investigated. X-ray photoelectron spectroscopy (XPS) study of N-doped graphene reveals that the highest doping level of 7.2% N is achieved at 180 Degree-Sign C for 12 h. N binding configurations of sample consist of pyridine N, quaternary N, and pyridine-N oxides. N doping is accompanied by the reduction of GO with decreases in oxygen levels from 34.8% in GO down to 8.5% in that of N-doped graphene. Meanwhile, the sample exhibits excellent N-doped thermal stability. Electrical measurements demonstrate that products have higher capacitive performance than that of pure graphene, the maximum specific capacitance of 144.6 F/g can be obtained which ascribe the pseudocapacitive effect from the N-doping. The samples also show excellent long-term cycle stability of capacitive performance.

Highly concentrated, stable nitrogen-doped graphene for supercapacitors: Simultaneous doping and reduction

Science.gov (United States)

Jiang, Baojiang; Tian, Chungui; Wang, Lei; Sun, Li; Chen, Chen; Nong, Xiaozhen; Qiao, Yingjie; Fu, Honggang

2012-02-01

In this work, we developed a concentrated ammonia-assisted hydrothermal method to obtain N-doped graphene sheets by simultaneous N-doping and reduction of graphene oxide (GO) sheets. The effects of hydrothermal temperature on the surface chemistry and the structure of N-doped graphene sheets were also investigated. X-ray photoelectron spectroscopy (XPS) study of N-doped graphene reveals that the highest doping level of 7.2% N is achieved at 180 °C for 12 h. N binding configurations of sample consist of pyridine N, quaternary N, and pyridine-N oxides. N doping is accompanied by the reduction of GO with decreases in oxygen levels from 34.8% in GO down to 8.5% in that of N-doped graphene. Meanwhile, the sample exhibits excellent N-doped thermal stability. Electrical measurements demonstrate that products have higher capacitive performance than that of pure graphene, the maximum specific capacitance of 144.6 F/g can be obtained which ascribe the pseudocapacitive effect from the N-doping. The samples also show excellent long-term cycle stability of capacitive performance.

Gemcitabine and capecitabine for heavily pre-treated metastatic colorectal cancer patients

DEFF Research Database (Denmark)

Spindler, Karen-Lise G; Pallisgaard, Niels; Andersen, Rikke F

2014-01-01

AIM: We investigated the efficacy and safety of capecitabine and gemcitabin (GemCap) in heavily pre-treated, therapy-resistant metastatic colorectal cancer (mCRC) patients and the clinical importance of cell-free DNA (cfDNA) measurement. PATIENTS AND METHODS: Patients' inclusion criteria included...

Activation and deactivation in heavily boron-doped silicon

International Nuclear Information System (INIS)

Yoo, Seung-Han; Ro, Jae-Sang

2003-01-01

A shallow p + /n junction was formed using a ultra-low-energy (ULE) implanter. Activation by rapid thermal annealing (RTA) exhibited both solid phase epitaxy, in which the sheet resistance dropped rapidly, and reverse annealing, in a manner similar to furnace annealing. The temperature ranges in which these phenomena were observed, however, were higher in the case of RTA processing than they were in the case of furnace annealing due to the low thermal budget associated with the former. Deactivation phenomena were investigated for the shallow source/drain junction based on measurements of the post-annealing time and temperature following the RTA treatments. We found that the deactivation kinetics was divided into two regions. In the first regions, the rate of deactivation increased exponentially with the annealing temperature up to 850 .deg. C. In the second regions, it was found to decrease linearly with the annealing temperature beyond 850 .deg. C. We believe that the first region is kinetically limited while the second is thermodynamically limited. We also observed 'transient enhanced deactivation' an anomalous increase in the sheet resistance during the early stage of annealing at temperatures higher than 800 .deg. C. The activation energy for transient enhanced deactivation was measured to be in the 1.75 ∼ 1.87 eV range while that for normal deactivation was found to be between 3.49 and 3.69 eV.

Health-enhancing doping controls

DEFF Research Database (Denmark)

Christiansen, Ask Vest

2010-01-01

Editorial published at International Network of Humanistic Doping Research (INHDR) website: http://www.doping.au.dk/en/online-resources/editorials/......Editorial published at International Network of Humanistic Doping Research (INHDR) website: http://www.doping.au.dk/en/online-resources/editorials/...

Sanctions for doping in sport

Directory of Open Access Journals (Sweden)

Mandarić Sanja

2014-01-01

Full Text Available Top-level sport imposes new and more demanding physical and psychological pressures, and the desire for competing, winning and selfassertion leads athletes into temptation to use prohibited substances in order to achieve the best possible results. Regardless of the fact that the adverse consequences of prohibited substances are well-known, prestige and the need to dominate sports arenas have led to their use in sports. Doping is one of the biggest issues in sport today, and the fight against it is a strategic objective on both global and national levels. World Anti-Doping Agency, the International Olympic Committee, international sports federations, national anti-doping agencies, national sports federations, as well as governments and their repressive apparatuses are all involved in the fight against doping in sport. This paper points to a different etymology and phenomenology of doping, the beginnings of doping in sport, sports doping scandals as well as the most important international instruments regulating this issue. Also, there is a special reference in this paper to the criminal and misdemeanor sanctions for doping in sport. In Serbia doping in sport is prohibited by the Law on Prevention of Doping in Sports which came into force in 2005 and which prescribes the measures and activities aimed at prevention of doping in sport. In this context, the law provides for the following three criminal offenses: use of doping substances, facilitating the use of doping substances, and unauthorized production and putting on traffic of doping substances. In addition, aiming at curbing the abuse of doping this law also provides for two violations. More frequent and repetitive doping scandals indicate that doping despite long-standing sanctions is still present in sports, which suggests that sanctions alone have not given satisfactory results so far.

Doped graphene supercapacitors

Science.gov (United States)

Ashok Kumar, Nanjundan; Baek, Jong-Beom

2015-12-01

Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed.

Doped graphene supercapacitors

International Nuclear Information System (INIS)

Kumar, Nanjundan Ashok; Baek, Jong-Beom

2015-01-01

Heteroatom-doped graphitic frameworks have received great attention in energy research, since doping endows graphitic structures with a wide spectrum of properties, especially critical for electrochemical supercapacitors, which tend to complement or compete with the current lithium-ion battery technology/devices. This article reviews the latest developments in the chemical modification/doping strategies of graphene and highlights the versatility of such heteroatom-doped graphitic structures. Their role as supercapacitor electrodes is discussed in detail. This review is specifically focused on the concept of material synthesis, techniques for electrode fabrication and metrics of performance, predominantly covering the last four years. Challenges and insights into the future research and perspectives on the development of novel electrode architectures for electrochemical supercapacitors based on doped graphene are also discussed. (topical review)

Synthesis of Doped and non-Doped Nano MgO Ceramic Membranes

Directory of Open Access Journals (Sweden)

Shiraz Labib

2013-12-01

Full Text Available Doped and non-doped MgO coated thin films on alumina substrates were prepared using a chelating sol-gel method under controlled conditions to prepare nanomaterials with unprecedented properties. The effect of doping of ZnO on thermal, surface and structural properties was investigated using DTA-TG, BET and XRD respectively. Also microstructural studies and coating thickness measurements of MgO thin film were conducted using SEM. An increase in the thermal stability of MgO with increasing ZnO doping percent was observed. The increase of ZnO doping percent showed a marked decrease in the average particle size of MgO powder as a result of the replacement of some Mg2+ by Zn2+ which has similar ionic radius as Mg2+. This decrease in particle size of MgO was also related to the decrease of the degree of MgO crystalinity. The increase of ZnO doping also showed a marked decrease in coating thickness values of the prepared membranes. This decrease was related to the  mechanism of ZnO doping into a MgO crystal lattice.

Borazino-Doped Polyphenylenes.

Science.gov (United States)

Marinelli, Davide; Fasano, Francesco; Najjari, Btissam; Demitri, Nicola; Bonifazi, Davide

2017-04-19

The divergent synthesis of two series of borazino-doped polyphenylenes, in which one or more aryl units are replaced by borazine rings, is reported for the first time, taking advantage of the decarbonylative [4 + 2] Diels-Alder cycloaddition reaction between ethynyl and tetraphenylcyclopentadienone derivatives. Because of the possibility of functionalizing the borazine core with different groups on the aryl substituents at the N and B atoms of the borazino core, we have prepared borazino-doped polyphenylenes featuring different doping dosages and orientations. To achieve this, two molecular modules were prepared: a core and a branching unit. Depending on the chemical natures of the central aromatic module and the reactive group, each covalent combination of the modules yields one exclusive doping pattern. By means of this approach, three- and hexa-branched hybrid polyphenylenes featuring controlled orientations and dosages of the doping B 3 N 3 rings have been prepared. Detailed photophysical investigations showed that as the doping dosage is increased, the strong luminescent signal is progressively reduced. This suggests that the presence of the B 3 N 3 rings engages additional deactivation pathways, possibly involving excited states with an increasing charge-separated character that are restricted in the full-carbon analogues. Notably, a strong effect of the orientational doping on the fluorescence quantum yield was observed for those hybrid polyphenylene structures featuring low doping dosages. Finally, we showed that Cu-catalyzed 1,3-dipolar cycloaddition is also chemically compatible with the BN core, further endorsing the inorganic benzene as a versatile aromatic scaffold for engineering of molecular materials with tailored and exploitable optoelectronic properties.

N-type polycrystalline silicon films formed on alumina by aluminium induced crystallization and overdoping

Energy Technology Data Exchange (ETDEWEB)

Tuezuen, O. [InESS, UMR 7163 CNRS-ULP, 23 rue du Loess, F-67037 Strasbourg (France)], E-mail: Ozge.Tuzun@iness.c-strasbourg.fr; Slaoui, A. [InESS, UMR 7163 CNRS-ULP, 23 rue du Loess, F-67037 Strasbourg (France); Gordon, I. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Focsa, A. [InESS, UMR 7163 CNRS-ULP, 23 rue du Loess, F-67037 Strasbourg (France); Ballutaud, D. [GEMaC-UMR 8635 CNRS, 1 place Aristide Briand, F-92195 Meudon (France); Beaucarne, G.; Poortmans, J. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium)

2008-08-30

In this work, we investigated the formation of n-type polysilicon films on alumina substrates by overdoping a p-type silicon layer obtained by aluminium induced crystallization of amorphous silicon (AIC), and subsequent epitaxy. The phosphorus doping of the AIC was carried out by thermal diffusion from a solid source. The structural quality of the n-type Si film was monitored by optical microscope and scanning electron microscope (SEM). The doping efficiency was determined by resistivity measurements and secondary ion mass spectroscopy (SIMS). The sheet resitivity changed from 2700{omega}/sq to 19.6{omega}/sq after thermal diffusion at 950 deg. C for 1h, indicating the overdoping effect. The SIMS profile carried out after the high temperature epitaxy exhibits a two steps phosphorus distribution, indicating the formation of an n{sup +}n structure.

Wafer-scale laser pantography: Fabrication of n-metal-oxide-semiconductor transistors and small-scale integrated circuits by direct-write laser-induced pyrolytic reactions

International Nuclear Information System (INIS)

McWilliams, B.M.; Herman, I.P.; Mitlitsky, F.; Hyde, R.A.; Wood, L.L.

1983-01-01

A complete set of processes sufficient for manufacture of n-metal-oxide-semiconductor (n-MOS) transistors by a laser-induced direct-write process has been demonstrated separately, and integrated to yield functional transistors. Gates and interconnects were fabricated of various combinations of n-doped and intrinsic polysilicon, tungsten, and tungsten silicide compounds. Both 0.1-μm and 1-μm-thick gate oxides were micromachined with and without etchant gas, and the exposed p-Si [100] substrate was cleaned and, at times, etched. Diffusion regions were doped by laser-induced pyrolytic decomposition of phosphine followed by laser annealing. Along with the successful manufacture of working n-MOS transistors and a set of elementary digital logic gates, this letter reports the successful use of several laser-induced surface reactions that have not been reported previously

Reversible and Precisely Controllable p/n-Type Doping of MoTe2 Transistors through Electrothermal Doping.

Science.gov (United States)

Chang, Yuan-Ming; Yang, Shih-Hsien; Lin, Che-Yi; Chen, Chang-Hung; Lien, Chen-Hsin; Jian, Wen-Bin; Ueno, Keiji; Suen, Yuen-Wuu; Tsukagoshi, Kazuhito; Lin, Yen-Fu

2018-03-01

Precisely controllable and reversible p/n-type electronic doping of molybdenum ditelluride (MoTe 2 ) transistors is achieved by electrothermal doping (E-doping) processes. E-doping includes electrothermal annealing induced by an electric field in a vacuum chamber, which results in electron (n-type) doping and exposure to air, which induces hole (p-type) doping. The doping arises from the interaction between oxygen molecules or water vapor and defects of tellurium at the MoTe 2 surface, and allows the accurate manipulation of p/n-type electrical doping of MoTe 2 transistors. Because no dopant or special gas is used in the E-doping processes of MoTe 2 , E-doping is a simple and efficient method. Moreover, through exact manipulation of p/n-type doping of MoTe 2 transistors, quasi-complementary metal oxide semiconductor adaptive logic circuits, such as an inverter, not or gate, and not and gate, are successfully fabricated. The simple method, E-doping, adopted in obtaining p/n-type doping of MoTe 2 transistors undoubtedly has provided an approach to create the electronic devices with desired performance. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theoretical study of bismuth-doped cadmium telluride

Science.gov (United States)

Menendez-Proupin, E.; Rios-Gonzalez, J. A.; Pena, J. L.

Cadmium telluride heavily doped with bismuth has been proposed as an absorber with an intermediate band for solar cells. Increase in the photocurrent has been shown recently, although the overall cell efficiency has not improved. In this work, we study the electronic structure and the formation energies of the defects associated to bismuth impurities. We have performed electronic structure calculations within generalized density functional theory, using the exchange-correlation functional HSE(w) , where the range-separation parameter w has been tuned to reproduce the CdTe bandgap. Improving upon previous reports, we have included the spin-orbit interaction, which modifies the structure of the valence band and the energy levels of bismuth. We have found that interstitial Bi (Bii) tends to occupy Cd vacancies, cadmium substitution (BiCd) creates single donor level, while tellurium substitution (BiTe) is a shallow single acceptor. We investigate the interaction between these point defects and how can they be combined to create a partially filled intermediate band. Supported by FONDECYT Grant 1130437, CONACYT-SENER SUSTENTABILIDAD ENERGETICA/project CeMIE-Sol PY-207450/25 and PY-207450/26. JARG acknowledges CONACYT fellowship for research visit. Powered@NLHPC (ECM-02).

Possible observation of the Berezinskii-Kosterlitz-Thouless transition in boron-doped diamond films

Science.gov (United States)

Coleman, Christopher; Bhattacharyya, Somnath

2017-11-01

The occurrence of the Berezinskii-Kosterlitz-Thouless (BKT) transition is investigated in heavily boron-doped nanocrystalline diamond films through a combination of current-voltage and resistance measurements. We observe transport features suggesting a robust BKT transition along with transport features related to vortex pinning in nanocrystalline diamond films with smaller grain size. The vortex core energy determined through analysis of the resistance temperature curves was found to be anti-correlated to the BKT transition temperatures. It is also observed that the higher BKT temperature is related to an increased vortex-antivortex binding energy derived from the activated transport regions. Further, the magnetic field induced superconductor insulator transition shows the possibility of the charge glass state. The consequences of granularity such as localization and vortex pinning can lead to tuneable BKT temperatures and strongly affects the field induced insulating state.

NuSTAR observations of heavily obscured quasars at z ~ 0.5

DEFF Research Database (Denmark)

Lansbury, G. B.; Alexander, D. M.; Del Moro, A.

2014-01-01

We present NuSTAR hard X-ray observations of three Type 2 quasars at z ≈ 0.4-0.5, optically selected from the Sloan Digital Sky Survey. Although the quasars show evidence for being heavily obscured, Compton-thick systems on the basis of the 2-10 keV to [O III] luminosity ratio and multiwavelength...

Doping droops.

Science.gov (United States)

Chaturvedi, Aditi; Chaturvedi, Harish; Kalra, Juhi; Kalra, Sudhanshu

2007-01-01

Drug abuse is a major concern in the athletic world. The misconception among athletes and their coaches is that when an athlete breaks a record it is due to some "magic ingredient" and not because of training, hard work, mental attitude and championship performance. The personal motivation to win in competitive sports has been intensified by national, political, professional and economic incentives. Under this increased pressure athletes have turned to finding this "magic ingredient". Athlete turns to mechanical (exercise, massage), nutritional (vitamins, minerals), pharmacological (medicines) or gene therapies to have an edge over other players. The World Anti-Doping Agency (WADA) has already asked scientists to help find ways to prevent gene therapy from becoming the newest form of doping. The safety of the life of athletes is compromised with all forms of doping techniques, be it a side effect of a drug or a new technique of gene doping.

Synthesis and Doping of Silicon Nanocrystals for Versatile Nanocrystal Inks

Science.gov (United States)

Kramer, Nicolaas Johannes

atmospheric pressures necessitates high plasma densities to reach temperatures required for crystallization of nanoparticles. Using experimentally determined plasma properties from the literature, the model estimates the nanoparticle temperature that is achieved during synthesis at atmospheric pressures. It was found that temperatures well above those required for crystallization can be achieved. Now that the synthesis of nanocrystals is understood, the second half of this thesis will focus on doping of the nanocrystals. The doping of semiconductor nanocrystals, which is vital for the optimization of nanocrystal-based devices, remains a challenge. Gas phase plasma approaches have been very successful in incorporating dopant atoms into nanocrystals by simply adding a dopant precursor during synthesis. However, little is known about the electronic activation of these dopants. This was investigated with field-effect transistor measurements using doped silicon nanocrystal films. It was found that, analogous to bulk silicon, boron and phosphorous electronically dope silicon nanocrystals. However, the dopant activation efficiency remains low as a result of self-purification of the dopants to the nanocrystal surface. Next the plasmonic properties of heavily doped silicon nanocrystals was explored. While the synthesis method was identical, the plasmonic behavior of phosphorus-doped and boron-doped nanocrystals was found the be significantly different. Phosphorus-doped nanocrystals exhibit a plasmon resonance immediately after synthesis, while boron-doped nanocrystals require a post-synthesis annealing or oxidation treatment. This is a result of the difference in dopant location. Phosphorus is more likely to be incorporated into the core of the nanocrystal, while the majority of boron is placed on the surface of the nanocrystal. The oxidized boron-doped particles exhibit stable plasmonic properties, and therefore this allows for the production of air-stable silicon-based plasmonic

Doping control in sport

DEFF Research Database (Denmark)

Overbye, Marie Birch

2016-01-01

Doping testing is a key component enforced by anti-doping authorities to detect and deter doping in sport. Policy is developed to protect athletes' right to participate in doping-free sport; and testing is a key tool to secure this right. Accordingly, athletes' responses to anti-doping efforts...... are important. This article explores how the International Standards for Testing, which face different interpretations and challenges when policy is implemented, are perceived by elite athletes. Particularly, this article aims to investigate how elite athletes perceive the functioning of the testing system (i.......e., the efforts of stakeholders involved in testing) in their own sport both nationally and worldwide. Moreover, it seeks to identify whether specific factors such as previous experience of testing and perceived proximity of doping have an impact on athletes' perceptions of the testing system. The study comprises...

Unusual photoelectric behaviors of Mo-doped TiO2 multilayer thin films prepared by RF magnetron co-sputtering: effect of barrier tunneling on internal charge transfer

Science.gov (United States)

Yan, B. X.; Luo, S. Y.; Mao, X. G.; Shen, J.; Zhou, Q. F.

2013-01-01

Mo-doped TiO2 multilayer thin films were prepared by RF magnetron co-sputtering. Microstructures, crystallite parameters and the absorption band were investigated with atomic force microscopy, X-ray diffraction and ultraviolet-visible spectroscopy. Internal carrier transport characteristics and the photoelectric property of different layer-assemble modes were examined on an electrochemical workstation under visible light. The result indicates that the double-layer structure with an undoped surface layer demonstrated a red-shifted absorption edge and a much stronger photocurrent compared to the uniformly doped sample, signifying that the electric field implanted at the interface between particles in different layers accelerated internal charge transfer effectively. However, a heavily doped layer implanted at the bottom of the three-layer film merely brought about negative effects on the photoelectric property, mainly because of the Schottky junction existing above the substrate. Nevertheless, this obstacle was successfully eliminated by raising the Mo concentration to 1020 cm-3, where the thickness of the depletion layer fell into the order of angstroms and the tunneling coefficient manifested a dramatic increase. Under this circumstance, the Schottky junction disappeared and the strongest photocurrent was observed in the three-layer film.

Numerical analysis of band tails in nanowires and their effects on the performance of tunneling field-effect transistors

Science.gov (United States)

Tanaka, Takahisa; Uchida, Ken

2018-06-01

Band tails in heavily doped semiconductors are one of the important parameters that determine transfer characteristics of tunneling field-effect transistors. In this study, doping concentration and doing profile dependences of band tails in heavily doped Si nanowires were analyzed by a nonequilibrium Green function method. From the calculated band tails, transfer characteristics of nanowire tunnel field-effect transistors were numerically analyzed by Wentzel–Kramer–Brillouin approximation with exponential barriers. The calculated transfer characteristics demonstrate that the band tails induced by dopants degrade the subthreshold slopes of Si nanowires from 5 to 56 mV/dec in the worst case. On the other hand, surface doping leads to a high drain current while maintaining a small subthreshold slope.

Doping Attitudes and Covariates of Potential Doping Behaviour in High-Level Team-Sport Athletes; Gender Specific Analysis

Science.gov (United States)

Sekulic, Damir; Tahiraj, Enver; Zvan, Milan; Zenic, Natasa; Uljevic, Ognjen; Lesnik, Blaz

2016-01-01

Team sports are rarely studied with regard to doping behaviour and doping-related factors regardless of their global popularity. This study aimed to investigate doping factors and covariates of potential doping behaviour in high-level team-sport athletes. The subjects were 457 high-performing, national- and international-level athletes (21.9 ± 3.4 years of age; 179 females) involved in volleyball (n = 77), soccer (n = 163), basketball (n = 114) and handball (n = 103). Previously validated self-administered questionnaires aimed at evidencing sport factors, doping-related factors, knowledge on sport nutrition and doping, and attitudes to performance enhancement were used. The results indicated a higher doping likelihood in male athletes, with a significant gender difference for basketball and handball. In males, a higher doping likelihood is found for athletes who had achieved better results at junior-age level, those who regularly consume dietary supplements, and who perceive their sport as being contaminated by doping. A higher sport achievement at senior-age level is protective against potential doping behaviour in males. In females, a higher likelihood of doping is evidenced in those athletes involved in binge drinking, while a lower tendency for doping is evidenced in female athletes who possess better knowledge on sport nutrition. Knowledge about doping is very low and thus education about doping is urgently needed. An improvement of knowledge on sport nutrition might be a potentially effective method for reducing the tendency for doping in females. Future studies should consider other approaches and theories, such as theory of planned behaviour and/or social-cognitive theory, in studying the problem of doping behaviour in team-sports. Key points The doping knowledge among Kosovar team-sport athletes is very low and systematic anti-doping education is urgently needed. The highest risk of doping behaviour in males is found for those athletes who had been

Doping of organic semiconductors

Energy Technology Data Exchange (ETDEWEB)

Luessem, B.; Riede, M.; Leo, K. [Institut fuer Angewandte Photophysik, TU Dresden (Germany)

2013-01-15

The understanding and applications of organic semiconductors have shown remarkable progress in recent years. This material class has been developed from being a lab curiosity to the basis of first successful products as small organic LED (OLED) displays; other areas of application such as OLED lighting and organic photovoltaics are on the verge of broad commercialization. Organic semiconductors are superior to inorganic ones for low-cost and large-area optoelectronics due to their flexibility, easy deposition, and broad variety, making tailor-made materials possible. However, electrical doping of organic semiconductors, i.e. the controlled adjustment of Fermi level that has been extremely important to the success of inorganic semiconductors, is still in its infancy. This review will discuss recent work on both fundamental principles and applications of doping, focused primarily to doping of evaporated organic layers with molecular dopants. Recently, both p- and n-type molecular dopants have been developed that lead to efficient and stable doping of organic thin films. Due to doping, the conductivity of the doped layers increases several orders of magnitude and allows for quasi-Ohmic contacts between organic layers and metal electrodes. Besides reducing voltage losses, doping thus also gives design freedom in terms of transport layer thickness and electrode choice. The use of doping in applications like OLEDs and organic solar cells is highlighted in this review. Overall, controlled molecular doping can be considered as key enabling technology for many different organic device types that can lead to significant improvements in efficiencies and lifetimes. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Doping of organic semiconductors

International Nuclear Information System (INIS)

Luessem, B.; Riede, M.; Leo, K.

2013-01-01

The understanding and applications of organic semiconductors have shown remarkable progress in recent years. This material class has been developed from being a lab curiosity to the basis of first successful products as small organic LED (OLED) displays; other areas of application such as OLED lighting and organic photovoltaics are on the verge of broad commercialization. Organic semiconductors are superior to inorganic ones for low-cost and large-area optoelectronics due to their flexibility, easy deposition, and broad variety, making tailor-made materials possible. However, electrical doping of organic semiconductors, i.e. the controlled adjustment of Fermi level that has been extremely important to the success of inorganic semiconductors, is still in its infancy. This review will discuss recent work on both fundamental principles and applications of doping, focused primarily to doping of evaporated organic layers with molecular dopants. Recently, both p- and n-type molecular dopants have been developed that lead to efficient and stable doping of organic thin films. Due to doping, the conductivity of the doped layers increases several orders of magnitude and allows for quasi-Ohmic contacts between organic layers and metal electrodes. Besides reducing voltage losses, doping thus also gives design freedom in terms of transport layer thickness and electrode choice. The use of doping in applications like OLEDs and organic solar cells is highlighted in this review. Overall, controlled molecular doping can be considered as key enabling technology for many different organic device types that can lead to significant improvements in efficiencies and lifetimes. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

DOPING CONTROL AND LIABILITY FOR THE USE OF DOPING IN SPORT

Directory of Open Access Journals (Sweden)

Lyudmila Aleksandrovna Kiryanova

2017-10-01

Full Text Available Purpose. The article is devoted to the use by athletes of different performance enhancing drugs and banned anabolic steroids to enhance athletic performance. Authors aim to justify the improvement of the Russian legislation and anti-doping education. Methodology. The study constitutes an analysis of the legal documents of international standards and Russian legislation, the formulation of the concept of “doping”, the definition of the role of WADA in the development of anti-doping information and education programs for young generation of athletes. The authors identified pedagogical and organizational issues of the fight against doping in sport. Results. The studies found that an important thing of educational work is the pedagogical aspect. The authors have developed anti-doping activities that are recommended for use in the system of youth sports and education in the universities of physical culture. Practical implications. The results of the study are recommended for use in educational techniques anti-doping character in the sphere of physical culture and sports.

First-principles study of doping effect on the phase transition of zinc oxide with transition metal doped

International Nuclear Information System (INIS)

Wu, Liang; Hou, Tingjun; Wang, Yi; Zhao, Yanfei; Guo, Zhenyu; Li, Youyong; Lee, Shuit-Tong

2012-01-01

Highlights: ► We study the doping effect on B4, B1 structures and phase transition of ZnO. ► We calculate the phase transition barrier and phase transition path of doped ZnO. ► The transition metal doping decreases the bulk modulus and phase transition pressure. ► The magnetic properties are influenced by the phase transition process. - Abstract: Zinc oxide (ZnO) is a promising material for its wide application in solid-state devices. With the pressure raised from an ambient condition, ZnO transforms from fourfold wurtzite (B4) to sixfold coordinated rocksalt (B1) structure. Doping is an efficient approach to improve the structures and properties of materials. Here we use density-functional theory (DFT) to study doped ZnO and find that the transition pressure from B4 phase to B1 phase of ZnO always decreases with different types of transition metal (V, Cr, Mn, Fe, Co, or Ni) doped, but the phase transition path is not affected by doping. This is consistent with the available experimental results for Mn-doped ZnO and Co-doped ZnO. Doping in ZnO causes the lattice distortion, which leads to the decrease of the bulk modulus and accelerates the phase transition. Mn-doped ZnO shows the strongest magnetic moment due to its half filled d orbital. For V-doped ZnO and Cr-doped ZnO, the magnetism is enhanced by phase transition from B4 to B1. But for Mn-doped ZnO, Fe-doped ZnO, Co-doped ZnO, and Ni-doped ZnO, B1 phase shows weaker magnetic moment than B4 phase. These results can be explained by the amount of charge transferred from the doped atom to O atom. Our results provide a theoretical basis for the doping approach to change the structures and properties of ZnO.

High p-type doping, mobility, and photocarrier lifetime in arsenic-doped CdTe single crystals

Science.gov (United States)

Nagaoka, Akira; Kuciauskas, Darius; McCoy, Jedidiah; Scarpulla, Michael A.

2018-05-01

Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 1016 and 1020 cm-3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 1017 cm-3 is presented, while for higher-doped samples, precipitation of a second phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20-30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm2/Vs at room temperature. A doping limit in the low 1017/cm3 range is observed for samples quenched at 200-300 °C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 1016 cm-3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 1018 cm-3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.

Knowledge of pharmacy students about doping, and the need for doping education: a questionnaire survey.

Science.gov (United States)

Shibata, Keita; Ichikawa, Koichi; Kurata, Naomi

2017-08-11

Anti-doping activities are carried out on a global scale. Based on these activities, the specialty of "sports pharmacist," which entails a deeper comprehension of doping, use of supplements, and appropriate drug use for athletes, was established in 2009 in Japan. It is difficult to say whether the education on doping is adequate for pharmacy students who will be eligible to become sports pharmacists. It is also unclear how well these students understand doping. Therefore, the aim of this study was to investigate pharmacy students' current knowledge of appropriate drug use, doping and use of supplements, and to explore the need for further education on these topics. A questionnaire survey was conducted from July 3rd to August 2nd in 2014 at Showa University in Japan. A total of 406 respondents (2nd- to 6th-year students) were assessed as eligible. Group comparison was used to compare those who had attended a lecture about doping and those who had not. Most of the students only knew the word doping and had not attended a lecture on the subject, but 72% of them expressed a desire to attend one. Over half did not know that the most common doping violation in Japan is unintentional doping, and were unfamiliar with certain past cases of doping. In addition, 41% did not know that over-the-counter medicines and dietary supplements might contain prohibited substances, and 87% were unaware that names of prohibited substances might not appear on the ingredient labels of dietary supplements. In contrast, attending a lecture on doping was effective in facilitating the acquisition of all these types of knowledge. It is important to provide more opportunities for appropriate education of pharmacy students on the topic of doping, given that interest exists and attending a lecture on the topic appears to be useful. More education about doping for pharmacy students would be as effective for anti-doping activities as is education of athletes.

Doping Attitudes and Covariates of Potential Doping Behaviour in High-Level Team-Sport Athletes; Gender Specific Analysis

Directory of Open Access Journals (Sweden)

Damir Sekulic, Enver Tahiraj, Milan Zvan, Natasa Zenic, Ognjen Uljevic, Blaz Lesnik

2016-12-01

Full Text Available Team sports are rarely studied with regard to doping behaviour and doping-related factors regardless of their global popularity. This study aimed to investigate doping factors and covariates of potential doping behaviour in high-level team-sport athletes. The subjects were 457 high-performing, national- and international-level athletes (21.9 ± 3.4 years of age; 179 females involved in volleyball (n = 77, soccer (n = 163, basketball (n = 114 and handball (n = 103. Previously validated self-administered questionnaires aimed at evidencing sport factors, doping-related factors, knowledge on sport nutrition and doping, and attitudes to performance enhancement were used. The results indicated a higher doping likelihood in male athletes, with a significant gender difference for basketball and handball. In males, a higher doping likelihood is found for athletes who had achieved better results at junior-age level, those who regularly consume dietary supplements, and who perceive their sport as being contaminated by doping. A higher sport achievement at senior-age level is protective against potential doping behaviour in males. In females, a higher likelihood of doping is evidenced in those athletes involved in binge drinking, while a lower tendency for doping is evidenced in female athletes who possess better knowledge on sport nutrition. Knowledge about doping is very low and thus education about doping is urgently needed. An improvement of knowledge on sport nutrition might be a potentially effective method for reducing the tendency for doping in females. Future studies should consider other approaches and theories, such as theory of planned behaviour and/or social-cognitive theory, in studying the problem of doping behaviour in team-sports.

On single doping and co-doping of spray pyrolysed ZnO films: Structural, electrical and optical characterisation

International Nuclear Information System (INIS)

Vimalkumar, T.V.; Poornima, N.; Jinesh, K.B.; Kartha, C. Sudha; Vijayakumar, K.P.

2011-01-01

In this paper we present studies on ZnO thin films (prepared using Chemical Spray pyrolysis (CSP) technique) doped in two different ways; in one set, 'single doping' using indium was done while in the second set, 'co-doping' using indium and fluorine was adopted. In the former case, effect of in-situ as well as ex-situ doping using In was analyzed. Structural (XRD studies), electrical (I-V measurements) and optical characterizations (through absorption, transmission and photoluminescence studies) of the films were done. XRD analysis showed that, for spray-deposited ZnO films, ex-situ doping using Indium resulted in preferred (0 0 2) plane orientation, while in-situ doping caused preferred orientation along (1 0 0), (0 0 2), (1 0 1) planes; however for higher percentage of in-situ doping, orientation of grains changed from (0 0 2) plane to (1 0 1) plane. The co-doped films had (0 0 2) and (1 0 1) planes. Lowest resistivity (2 x 10 -3 Ω cm) was achieved for the films, doped with 1% Indium through in-situ method. Photoluminescence (PL) emissions of ex-situ doped and co-doped samples had two peaks; one was the 'near band edge' emission (NBE) and the other was the 'blue-green' emission. But interestingly the PL emission of in-situ doped samples exhibited only the 'near band edge' emission. Optical band gap of the films increased with doping percentage, in all cases of doping.

High p-Type Doping, Mobility, and Photocarrier Lifetime in Arsenic-Doped CdTe Single Crystals

Energy Technology Data Exchange (ETDEWEB)

Kuciauskas, Darius [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Nagaoka, Akira [Kyoto University; University of Utah; McCoy, Jedidiah [Washington State University; Scarpulla, Michael A. [University of Utah

2018-05-08

Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 10^16 and 10^20 cm-3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 10^17 cm-3 is presented, while for higher-doped samples, precipitation of a second phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20-30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm2/Vs at room temperature. A doping limit in the low 10^17/cm3 range is observed for samples quenched at 200-300 degrees C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 10^16 cm-3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 10^18 cm-3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.

Enhanced B doping in CVD-grown GeSn:B using B δ-doping layers

Science.gov (United States)

Kohen, David; Vohra, Anurag; Loo, Roger; Vandervorst, Wilfried; Bhargava, Nupur; Margetis, Joe; Tolle, John

2018-02-01

Highly doped GeSn material is interesting for both electronic and optical applications. GeSn:B is a candidate for source-drain material in future Ge pMOS device because Sn adds compressive strain with respect to pure Ge, and therefore can boost the Ge channel performances. A high B concentration is required to obtain low contact resistivity between the source-drain material and the metal contact. To achieve high performance, it is therefore highly desirable to maximize both the Sn content and the B concentration. However, it has been shown than CVD-grown GeSn:B shows a trade-off between the Sn incorporation and the B concentration (increasing B doping reduces Sn incorporation). Furthermore, the highest B concentration of CVD-grown GeSn:B process reported in the literature has been limited to below 1 × 1020 cm-3. Here, we demonstrate a CVD process where B δ-doping layers are inserted in the GeSn layer. We studied the influence of the thickness between each δ-doping layers and the δ-doping layers process conditions on the crystalline quality and the doping density of the GeSn:B layers. For the same Sn content, the δ-doping process results in a 4-times higher B doping than the co-flow process. In addition, a B doping concentration of 2 × 1021 cm-3 with an active concentration of 5 × 1020 cm-3 is achieved.

Doping and musculoskeletal system: short-term and long-lasting effects of doping agents.

Science.gov (United States)

Nikolopoulos, Dimitrios D; Spiliopoulou, Chara; Theocharis, Stamatios E

2011-10-01

Doping is a problem that has plagued the world of competition and sports for ages. Even before the dawn of Olympic history in ancient Greece, competitors have looked for artificial means to improve athletic performance. Since ancient times, athletes have attempted to gain an unfair competitive advantage through the use of doping substances. A Prohibited List of doping substances and methods banned in sports is published yearly by the World Anti-Doping Agency. Among the substances included are steroidal and peptide hormones and their modulators, stimulants, glucocorticosteroids, β₂-agonists, diuretics and masking agents, narcotics, and cannabinoids. Blood doping, tampering, infusions, and gene doping are examples of prohibited methods indicated on the List. Apart from the unethical aspect of doping, as it abrogates fair-play's principle, it is extremely important to consider the hazards it presents to the health and well-being of athletes. The referred negative effects for the athlete's health have to do, on the one hand, by the high doses of the performance-enhancing agents and on the other hand, by the relentless, superhuman strict training that the elite or amateur athletes put their muscles, bones, and joints. The purpose of this article is to highlight the early and the long-lasting consequences of the doping abuse on bone and muscle metabolism. © 2010 The Authors Fundamental and Clinical Pharmacology © 2010 Société Française de Pharmacologie et de Thérapeutique.

Effects of Different Doping Ratio of Cu Doped CdS on QDSCs Performance

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Xiaojun Zhu

2015-01-01

Full Text Available We use the successive ionic layer adsorption and reaction (SILAR method for the preparation of quantum dot sensitized solar cells, to improve the performance of solar cells by doping quantum dots. We tested the UV-Vis absorption spectrum of undoped CdS QDSCs and Cu doped CdS QDSCs with different doping ratios. The doping ratios of copper were 1 : 100, 1 : 500, and 1 : 1000, respectively. The experimental results show that, under the same SILAR cycle number, Cu doped CdS quantum dot sensitized solar cells have higher open circuit voltage, short circuit current density photoelectric conversion efficiency than undoped CdS quantum dots sensitized solar cells. Refinement of Cu doping ratio are 1 : 10, 1 : 100, 1 : 200, 1 : 500, and 1 : 1000. When the proportion of Cu and CdS is 1 : 10, all the parameters of the QDSCs reach the minimum value, and, with the decrease of the proportion, the short circuit current density, open circuit voltage, and the photoelectric conversion efficiency are all increased. When proportion is 1 : 500, all parameters reach the maximum values. While with further reduction of the doping ratio of Cu, the parameters of QDSCs have a decline tendency. The results showed that, in a certain range, the lower the doping ratio of Cu, the better the performance of quantum dot sensitized solar cell.

Intermediate band mobility in heavily titanium-doped silicon layers

Energy Technology Data Exchange (ETDEWEB)

Gonzalez-Diaz, G.; Olea, J.; Martil, I.; Pastor, D. [Dpto. de Fisica Aplicada III (Electricidad y Electronica), Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, 28040 Madrid (Spain); Marti, A.; Antolin, E.; Luque, A [Instituto de Energia Solar, Universidad Politecnica de Madrid, Escuela Tecnica Superior de Ingenieros de Telecomunicacion, Ciudad Universitaria sn, 28040 Madrid (Spain)

2009-09-15

The sheet resistance and the Hall mobility of high-purity Si wafers, in whose surface Ti atoms are implanted and laser annealed reaching concentrations above 10{sup 21} cm{sup -3}, are measured in the 90-370 K range. Below 240 K, an unconventional behavior is observed that is well explained on the basis of the appearance of an intermediate band (IB) region able to form a blocking junction with the substrate and of the appearance of an IB conduction. Explanations based on ordinary device physics fail to justify all the unconventional behavior of the characteristics observed. (author)

Yield strength of a heavily drawn Cu-20% Nb filamentary microcomposite

International Nuclear Information System (INIS)

Hong, S.I.

1998-01-01

It has been well documented that heavily-drawn, copper-niobium microcomposites possess high strength and high conductivity. Since niobium has little solubility in copper, the conductivity of the copper is not strongly affected by the addition of niobium. Following extensive mechanical deformation of Cu-Nb, niobium dendrites transform into fine niobium ribbons as a result of the niobium texture upon drawing. This nanostructure contributes to the ultrahigh strength of Cu-Nb microcomposites. The strength of heavily deformed Cu-Nb exceeds that predicted by the rule-of-mixtures (ROM), and a fundamental understanding of the strengthening mechanisms involved has been the subject of much discussion. Spitzig and his coworkers suggests a barrier strengthening model while Funkenbusch and Courtney believe that stored dislocations have a role in substructural hardening. Hangen and Raabe recently proposed an analytical model for the calculation of the yield strength of Cu-Nb microcomposite. The model of Hangen and Raabe and that of Spitzig and his coworkers have a great deal of resemblance since both models attribute the strength to the difficulty of propagating plastic flow through the interface. The purpose of this study was to enhance the understanding of the strengthening mechanisms associated with Cu-Nb microcomposites by examining the previous studies on mechanical and microstructural stability of Cu-based microcomposites

DOPING IN SPORT: GLOBAL ETHICAL ISSUES

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Angela J. Schneider

2007-09-01

Full Text Available DESCRIPTION In this book the question of "How ethical is using performance improving drugs in sport?" is argued in global perspective. PURPOSE The ethical questions in sport are discussed comprehensively. Particularly, different cultures and approach of various countries to that issue were examined. FEATURES The book composed of 10 chapters following a thorough introduction from the editors in 194 pages. The titles are: 1.Fair is Fair, Or Is It? : A Moral Consideration of the Doping Wars in American Sport; 2.Are Doping Sanctions Justified? A Moral Relativistic View; 3.Cultural Nuances: Doping, Cycling and the Tour de France; 4.On Transgendered Athletes, Fairness and Doping: An International Challenge; 5.Creating a Corporate Anti-doping Culture: The Role of Bulgarian Sports Governing Bodies; 6. Doping in the UK: Alain and Dwain, Rio and Greg - Not Guilty?; 7.The Japanese Debate Surrounding the Doping Ban: The Application of the Harm Principle; 8. Doping and Anti-doping in Sport in China: An Analysis of Recent and Present Attitudes and Actions; 9.Anti-doping in Sport: The Norwegian Perspective; 10.Ethics in Sport: The Greek Educational Perspective on Anti-doping. AUDIENCE Given that this book is about a popular topic in sport, it is a great interest to the sport public as well as students, researchers and practitioners in the sport and exercise disciplines.

Gene doping.

Science.gov (United States)

Haisma, H J; de Hon, O

2006-04-01

Together with the rapidly increasing knowledge on genetic therapies as a promising new branch of regular medicine, the issue has arisen whether these techniques might be abused in the field of sports. Previous experiences have shown that drugs that are still in the experimental phases of research may find their way into the athletic world. Both the World Anti-Doping Agency (WADA) and the International Olympic Committee (IOC) have expressed concerns about this possibility. As a result, the method of gene doping has been included in the list of prohibited classes of substances and prohibited methods. This review addresses the possible ways in which knowledge gained in the field of genetic therapies may be misused in elite sports. Many genes are readily available which may potentially have an effect on athletic performance. The sporting world will eventually be faced with the phenomena of gene doping to improve athletic performance. A combination of developing detection methods based on gene arrays or proteomics and a clear education program on the associated risks seems to be the most promising preventive method to counteract the possible application of gene doping.

AFM of metallic nano-particles and nano-structures in heavily irradiated NaCl

NARCIS (Netherlands)

Gaynutdinov, R; Vainshtein, DI; Hak, SJ; Tolstikhina, A; Den Hartog, HW

2003-01-01

AFM investigations are reported for heavily, electron irradiated NaCl crystals in ultra high vacuum (UHV) in the non-contact mode-with an UHV AFM/STM Omicron system. To avoid chemical reactions between the radiolytic Na and oxygen and water, the irradiated samples were cleaved and prepared for the

Tracking with heavily irradiated silicon detectors operated at cryogenic temperatures

International Nuclear Information System (INIS)

Casagrande, L.; Barnett, B.M.; Bartalina, P.

1999-01-01

In this work, the authors show that a heavily irradiated double-sided silicon microstrip detector recovers its performance when operated at cryogenic temperatures. A DELPHI microstrip detector, irradiated to a fluence of ∼4 x 10 14 p/cm 2 , no longer operational at room temperature, cannot be distinguished from a non-irradiated one when operated at T < 120 K. Besides confirming the previously observed Lazarus effect in single diodes, these results establish, for the first time, the possibility of using standard silicon detectors for tracking applications in extremely demanding radiation environments

Current anti-doping policy: a critical appraisal.

Science.gov (United States)

Kayser, Bengt; Mauron, Alexandre; Miah, Andy

2007-03-29

Current anti-doping in competitive sports is advocated for reasons of fair-play and concern for the athlete's health. With the inception of the World Anti Doping Agency (WADA), anti-doping effort has been considerably intensified. Resources invested in anti-doping are rising steeply and increasingly involve public funding. Most of the effort concerns elite athletes with much less impact on amateur sports and the general public. We review this recent development of increasingly severe anti-doping control measures and find them based on questionable ethical grounds. The ethical foundation of the war on doping consists of largely unsubstantiated assumptions about fairness in sports and the concept of a "level playing field". Moreover, it relies on dubious claims about the protection of an athlete's health and the value of the essentialist view that sports achievements reflect natural capacities. In addition, costly antidoping efforts in elite competitive sports concern only a small fraction of the population. From a public health perspective this is problematic since the high prevalence of uncontrolled, medically unsupervised doping practiced in amateur sports and doping-like behaviour in the general population (substance use for performance enhancement outside sport) exposes greater numbers of people to potential harm. In addition, anti-doping has pushed doping and doping-like behaviour underground, thus fostering dangerous practices such as sharing needles for injection. Finally, we argue that the involvement of the medical profession in doping and anti-doping challenges the principles of non-maleficience and of privacy protection. As such, current anti-doping measures potentially introduce problems of greater impact than are solved, and place physicians working with athletes or in anti-doping settings in an ethically difficult position. In response, we argue on behalf of enhancement practices in sports within a framework of medical supervision. Current anti-doping

Attitudes and doping: a structural equation analysis of the relationship between athletes' attitudes, sport orientation and doping behaviour

Directory of Open Access Journals (Sweden)

Petróczi Andrea

2007-11-01

Full Text Available Abstract Background For effective deterrence methods, individual, systemic and situational factors that make an athlete or athlete group more susceptible to doping than others should be fully investigated. Traditional behavioural models assume that the behaviour in question is the ultimate end. However, growing evidence suggests that in doping situations, the doping behaviour is not the end but a means to an end, which is gaining competitive advantage. Therefore, models of doping should include and anti-doping policies should consider attitudes or orientations toward the specific target end, in addition to the attitude toward the 'tool' itself. Objectives The aim of this study was to empirically test doping related dispositions and attitudes of competitive athletes with the view of informing anti-doping policy developments and deterrence methods. To this end, the paper focused on the individual element of the drug availability – athlete's personality – situation triangle. Methods Data were collected by questionnaires containing a battery of psychological tests among competitive US male college athletes (n = 199. Outcome measures included sport orientation (win and goal orientation and competitiveness, doping attitude, beliefs and self-reported past or current use of doping. A structural equation model was developed based on the strength of relationships between these outcome measures. Results Whilst the doping model showed satisfactory fit, the results suggested that athletes' win and goal orientation and competitiveness do not play a statistically significant role in doping behaviour, but win orientation has an effect on doping attitude. The SEM analysis provided empirical evidence that sport orientation and doping behaviour is not directly related. Conclusion The considerable proportion of doping behaviour unexplained by the model suggests that other factors play an influential role in athletes' decisions regarding prohibited methods

Ba-DOPED ZnO MATERIALS: A DFT SIMULATION TO INVESTIGATE THE DOPING EFFECT ON FERROELECTRICITY

Directory of Open Access Journals (Sweden)

Luis H. da S. Lacerda

2016-04-01

Full Text Available ZnO is a semiconductor material largely employed in the development of several electronic and optical devices due to its unique electronic, optical, piezo-, ferroelectric and structural properties. This study evaluates the properties of Ba-doped wurtzite-ZnO using quantum mechanical simulations based on the Density Functional Theory (DFT allied to hybrid functional B3LYP. The Ba-doping caused increase in lattice parameters and slight distortions at the unit cell angle in a wurtzite structure. In addition, the doping process presented decrease in the band-gap (Eg at low percentages suggesting band-gap engineering. For low doping amounts, the wavelength characteristic was observed in the visible range; whereas, for middle and high doping amounts, the wavelength belongs to the Ultraviolet range. The Ba atoms also influence the ferroelectric property, which is improved linearly with the doping amount, except for doping at 100% or wurtzite-BaO. The ferroelectric results indicate the ZnO:Ba is an strong option to replace perovskite materials in ferroelectric and flash-type memory devices.

Gene doping in sports.

Science.gov (United States)

Unal, Mehmet; Ozer Unal, Durisehvar

2004-01-01

Gene or cell doping is defined by the World Anti-Doping Agency (WADA) as "the non-therapeutic use of genes, genetic elements and/or cells that have the capacity to enhance athletic performance". New research in genetics and genomics will be used not only to diagnose and treat disease, but also to attempt to enhance human performance. In recent years, gene therapy has shown progress and positive results that have highlighted the potential misuse of this technology and the debate of 'gene doping'. Gene therapies developed for the treatment of diseases such as anaemia (the gene for erythropoietin), muscular dystrophy (the gene for insulin-like growth factor-1) and peripheral vascular diseases (the gene for vascular endothelial growth factor) are potential doping methods. With progress in gene technology, many other genes with this potential will be discovered. For this reason, it is important to develop timely legal regulations and to research the field of gene doping in order to develop methods of detection. To protect the health of athletes and to ensure equal competitive conditions, the International Olympic Committee, WADA and International Sports Federations have accepted performance-enhancing substances and methods as being doping, and have forbidden them. Nevertheless, the desire to win causes athletes to misuse these drugs and methods. This paper reviews the current status of gene doping and candidate performance enhancement genes, and also the use of gene therapy in sports medicine and ethics of genetic enhancement. Copyright 2004 Adis Data Information BV

Doping dependence of charge order in electron-doped cuprate superconductors

Science.gov (United States)

Mou, Yingping; Feng, Shiping

2017-12-01

In the recent studies of the unconventional physics in cuprate superconductors, one of the central issues is the interplay between charge order and superconductivity. Here the mechanism of the charge-order formation in the electron-doped cuprate superconductors is investigated based on the t-J model. The experimentally observed momentum dependence of the electron quasiparticle scattering rate is qualitatively reproduced, where the scattering rate is highly anisotropic in momentum space, and is intriguingly related to the charge-order gap. Although the scattering strength appears to be weakest at the hot spots, the scattering in the antinodal region is stronger than that in the nodal region, which leads to the original electron Fermi surface is broken up into the Fermi pockets and their coexistence with the Fermi arcs located around the nodal region. In particular, this electron Fermi surface instability drives the charge-order correlation, with the charge-order wave vector that matches well with the wave vector connecting the hot spots, as the charge-order correlation in the hole-doped counterparts. However, in a striking contrast to the hole-doped case, the charge-order wave vector in the electron-doped side increases in magnitude with the electron doping. The theory also shows the existence of a quantitative link between the single-electron fermiology and the collective response of the electron density.

Ego involvement increases doping likelihood.

Science.gov (United States)

Ring, Christopher; Kavussanu, Maria

2018-08-01

Achievement goal theory provides a framework to help understand how individuals behave in achievement contexts, such as sport. Evidence concerning the role of motivation in the decision to use banned performance enhancing substances (i.e., doping) is equivocal on this issue. The extant literature shows that dispositional goal orientation has been weakly and inconsistently associated with doping intention and use. It is possible that goal involvement, which describes the situational motivational state, is a stronger determinant of doping intention. Accordingly, the current study used an experimental design to examine the effects of goal involvement, manipulated using direct instructions and reflective writing, on doping likelihood in hypothetical situations in college athletes. The ego-involving goal increased doping likelihood compared to no goal and a task-involving goal. The present findings provide the first evidence that ego involvement can sway the decision to use doping to improve athletic performance.

Structural, optical and magnetic properties of Mn doped ZnO thin films prepared by pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Aravind, Arun, E-mail: aruncusat@gmail.com [Nanophotonic and Optoelectronic Devices Laboratory, Department of Physics, Cochin University of Science and Technology, Kochi 682 022, Kerala (India); Jayaraj, M.K., E-mail: mkj@cusat.ac.in [Nanophotonic and Optoelectronic Devices Laboratory, Department of Physics, Cochin University of Science and Technology, Kochi 682 022, Kerala (India); Kumar, Mukesh; Chandra, Ramesh [Nano Science Laboratory, Institute Instrumentation Centre, IIT Roorkee, Roorkee 247 667, Uttarakhand (India)

2012-08-01

Highlights: Black-Right-Pointing-Pointer Defect induced Raman active modes in Mn doped ZnO thin films. Black-Right-Pointing-Pointer Room temperature ferromagnetism. Black-Right-Pointing-Pointer Morphological variations of ZnO thin films with Mn doping. Black-Right-Pointing-Pointer Variation of refractive index of ZnO thin films with Mn doping. - Abstract: Zn{sub 1-x}Mn{sub x}O thin films were grown by pulsed laser deposition. The phase purity and the structure were confirmed by X-ray diffraction studies. The films have a transmittance more than 80% in the visible region. The refractive index of Zn{sub 0.90}Mn{sub 0.10}O films is found to be 1.77 at 550 nm. The presence of non-polar E{sub 2}{sup high} and E{sub 2}{sup low} Raman modes in thin films indicates that 'Mn' doping does not change the wurtzite structure of ZnO. Apart from the normal modes of ZnO the Zn{sub 1-x}Mn{sub x}O ceramic targets show two additional modes at 332 cm{sup -1} (I{sub 1}) and 524 cm{sup -1} (I{sub 2}). The broad Raman peaks (340-600 cm{sup -1}) observed Zn{sub 0.90}Mn{sub 0.10}O thin films can be deconvoluted into five peaks, denoted as P{sub 1}-P{sub 5}. The possible origins of Raman peaks in Zn{sub 1-x}Mn{sub x}O films are the structural disorder and morphological change caused by the Mn dopant. The B{sub 1}{sup low}, {sup 2}B{sub 1}{sup low}, B{sub 1}{sup high} and A{sub 1}{sup LO} modes as well as the surface phonon mode have been observed in heavily Mn-doped ZnO films. Zn{sub 0.98}Mn{sub 0.02}O thin film shows room temperature ferromagnetism. The saturation magnetic moment of the Zn{sub 0.98}Mn{sub 0.02}O thin film is 0.42{mu}{sub B}/Mn atom. The undoped ZnO film prepared under the same condition shows diamagnetic nature. At higher doping concentrations the formation of Mn clusters suppress the room temperature ferromagnetism in Zn{sub 1-x}Mn{sub x}O thin films and shows paramagnetism. XPS confirms the incorporation of Mn{sup 2+} into the ZnO lattice.

Harmonization of anti-doping rules in a global context (World Anti-Doping Agency-laboratory accreditation perspective).

Science.gov (United States)

Ivanova, Victoria; Miller, John H M; Rabin, Olivier; Squirrell, Alan; Westwood, Steven

2012-07-01

This article provides a review of the leading role of the World Anti-Doping Agency (WADA) in the context of the global fight against doping in sport and the harmonization of anti-doping rules worldwide through the implementation of the World Anti-Doping Program. Particular emphasis is given to the WADA-laboratory accreditation program, which is coordinated by the Science Department of WADA in conjunction with the Laboratory Expert Group, and the cooperation with the international accreditation community through International Laboratory Accreditation Cooperation and other organizations, all of which contribute to constant improvement of laboratory performance in the global fight against doping in sport. A perspective is provided of the means to refine the existing anti-doping rules and programs to ensure continuous improvement in order to face growing sophisticated challenges. A viewpoint on WADA's desire to embrace cooperation with other international organizations whose knowledge can contribute to the fight against doping in sport is acknowledged.

Genetic doping and health damages.

Science.gov (United States)

Fallahi, Aa; Ravasi, Aa; Farhud, Dd

2011-01-01

Use of genetic doping or gene transfer technology will be the newest and the lethal method of doping in future and have some unpleasant consequences for sports, athletes, and outcomes of competitions. The World Anti-Doping Agency (WADA) defines genetic doping as "the non-therapeutic use of genes, genetic elements, and/or cells that have the capacity to enhance athletic performance ". The purpose of this review is to consider genetic doping, health damages and risks of new genes if delivered in athletes. This review, which is carried out by reviewing relevant publications, is primarily based on the journals available in GOOGLE, ELSEVIER, PUBMED in fields of genetic technology, and health using a combination of keywords (e.g., genetic doping, genes, exercise, performance, athletes) until July 2010. There are several genes related to sport performance and if they are used, they will have health risks and sever damages such as cancer, autoimmunization, and heart attack.

Controlling Molecular Doping in Organic Semiconductors.

Science.gov (United States)

Jacobs, Ian E; Moulé, Adam J

2017-11-01

The field of organic electronics thrives on the hope of enabling low-cost, solution-processed electronic devices with mechanical, optoelectronic, and chemical properties not available from inorganic semiconductors. A key to the success of these aspirations is the ability to controllably dope organic semiconductors with high spatial resolution. Here, recent progress in molecular doping of organic semiconductors is summarized, with an emphasis on solution-processed p-type doped polymeric semiconductors. Highlighted topics include how solution-processing techniques can control the distribution, diffusion, and density of dopants within the organic semiconductor, and, in turn, affect the electronic properties of the material. Research in these areas has recently intensified, thanks to advances in chemical synthesis, improved understanding of charged states in organic materials, and a focus on relating fabrication techniques to morphology. Significant disorder in these systems, along with complex interactions between doping and film morphology, is often responsible for charge trapping and low doping efficiency. However, the strong coupling between doping, solubility, and morphology can be harnessed to control crystallinity, create doping gradients, and pattern polymers. These breakthroughs suggest a role for molecular doping not only in device function but also in fabrication-applications beyond those directly analogous to inorganic doping. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dynamical spin susceptibility of electron-doped high-Tc cuprates. Comparison with hole-doped systems

International Nuclear Information System (INIS)

Suzuki, Atsuo; Mutou, Tetsuya; Tanaka, Syunsuke; Hirashima, Dai S.

2010-01-01

The magnetic excitation spectrum of electron-doped copper oxide superconductors is studied by calculating the dynamical spin susceptibility of the two-dimensional Hubbard model in which a d x2-y2 -wave superconducting order parameter is assumed. The spectrum of electron-doped systems is compared with that of hole-doped systems, and the relationship between the frequency at which a peak grows in the spectrum and the superconducting energy gap at a hot spot is investigated. A peak may be observed even when the magnetic resonance condition is not exactly satisfied. We find that, in the electron-doped systems, the resonance condition is less likely to be satisfied than in the hole-doped systems because of the small density of states around the hot spots, and the peak frequency is close to twice the gap magnitude at the hot spots. (author)

Hybrid Doping of Few-Layer Graphene via a Combination of Intercalation and Surface Doping

KAUST Repository

Mansour, Ahmed

2017-05-23

Surface molecular doping of graphene has been shown to modify its work function and increase its conductivity. However, the associated shifts in work function and increases in carrier concentration are highly coupled and limited by the surface coverage of dopant molecules on graphene. Here we show that few-layer graphene (FLG) can be doped using a hybrid approach, effectively combining surface doping by larger (metal-)organic molecules, while smaller molecules, such as Br2 and FeCl3, intercalate into the bulk. Intercalation tunes the carrier concentration more effectively, whereas surface doping of intercalated FLG can be used to tune its work function without reducing the carrier mobility. This multi-modal doping approach yields a very high carrier density and tunable work function for FLG, demonstrating a new versatile platform for fabricating graphene-based contacts for electronic, optoelectronic and photovoltaic applications.

Hybrid Doping of Few-Layer Graphene via a Combination of Intercalation and Surface Doping

KAUST Repository

Mansour, Ahmed; Kirmani, Ahmad R.; Barlow, Stephen; Marder, Seth R.; Amassian, Aram

2017-01-01

Surface molecular doping of graphene has been shown to modify its work function and increase its conductivity. However, the associated shifts in work function and increases in carrier concentration are highly coupled and limited by the surface coverage of dopant molecules on graphene. Here we show that few-layer graphene (FLG) can be doped using a hybrid approach, effectively combining surface doping by larger (metal-)organic molecules, while smaller molecules, such as Br2 and FeCl3, intercalate into the bulk. Intercalation tunes the carrier concentration more effectively, whereas surface doping of intercalated FLG can be used to tune its work function without reducing the carrier mobility. This multi-modal doping approach yields a very high carrier density and tunable work function for FLG, demonstrating a new versatile platform for fabricating graphene-based contacts for electronic, optoelectronic and photovoltaic applications.

Doping of III-nitride materials

OpenAIRE

Pampili, Pietro; Parbrook, Peter J.

2016-01-01

In this review paper we will report the current state of research regarding the doping of III-nitride materials and their alloys. GaN is a mature material with both n-type and p-type doping relatively well understood, and while n-GaN is easily achieved, p-type doping requires much more care. There are significant efforts to extend the composition range that can be controllably doped for AlGaInN alloys. This would allow application in shorter and longer wavelength optoelectronics as well as ex...

Photocatalysis with chromium-doped TiO2: Bulk and surface doping

KAUST Repository

Ould-Chikh, Samy

2014-04-15

The photocatalytic properties of TiO2 modified by chromium are usually found to depend strongly on the preparation method. To clarify this problem, two series of chromium-doped titania with a chromium content of up to 1.56 wt % have been prepared under hydrothermal conditions: the first series (Cr:TiO2) is intended to dope the bulk of TiO2, whereas the second series (Cr/TiO2) is intended to load the surface of TiO2 with Cr. The catalytic properties have been compared in the photocatalytic oxidation of formic acid. Characterization data provides evidence that in the Cr/TiO2 catalysts chromium is located on the surface of TiO2 as amorphous CrOOH clusters. In contrast, in the Cr:TiO 2 series, chromium is mostly dissolved in the titania lattice, although a minor part is still present on the surface. Photocatalytic tests show that both series of chromium-doped titania demonstrate visible-light-driven photo-oxidation activity. Surface-doped Cr/TiO2 solids appear to be more efficient photocatalysts than the bulk-doped Cr:TiO2 counterparts. It\\'s classified! The photocatalytic properties of TiO2 modified by chromium depend strongly on the preparation method. To clarify this problem, two types of modified titania are discussed: one with CrIII doped in the bulk and one with CrOOH clusters on the TiO2 surface (see picture). Both series show visible-light-driven photo-oxidation activity. However, surface modification appears to be a more efficient strategy. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An X-ray wave theory for heavily distorted crystals. 1

International Nuclear Information System (INIS)

Ohkawa, T.; Hashimoto, H.

1985-01-01

An X-ray diffraction theory is developed of monochromatic waves having spherical wave front, which is applicable to an interpretation of divergent X-ray diffraction images of crystals containing arbitral types of strain field. The theory is divided into two parts. In part I, Takagi's theory is expanded by introducing amplitude and phase correction functions and a new improved representation for the X-ray diffraction theory is given. In part II dispersion surfaces in heavily distorted crystals are discussed, and in the discussion the resonance shift functions are introduced. These formulations can lead to a complete understanding of the extinction phenomena. (author)

Biomarker monitoring in sports doping control.

Science.gov (United States)

Pottgiesser, Torben; Schumacher, Yorck Olaf

2012-06-01

Biomarker monitoring can be considered a new era in the effort against doping. Opposed to the old concept in doping control of direct detection of a prohibited substance in a biological sample such as urine or blood, the new paradigm allows a personalized longitudinal monitoring of biomarkers that indicate non-physiological responses independently of the used doping technique or substance, and may cause sanctioning of illicit practices. This review presents the development of biomarker monitoring in sports doping control and focuses on the implementation of the Athlete Biological Passport as the current concept of the World Anti Doping Agency for the detection of blood doping (hematological module). The scope of the article extends to the description of novel biomarkers and future concepts of application.

[Doping. High-tech cheating in sport].

Science.gov (United States)

Striegel, H; Simon, P

2007-07-01

Today, doping is no longer limited to the classical drugs with well known effects and side effects. Older generation anabolic steroids are used mainly in fitness and recreational sports. In contrast, due to doping tests, substances used in competitive sports include peptide hormones, medications not yet approved, and even specially developed drugs, such as designer steroids. Of the peptide hormones, particularly growth hormones (human growth hormone), erythropoietin and generics, insulin, and presumably insulin-like growth factor 1 are used. Substance groups potentially relevant for doping are selective androgen receptor modulators and gene therapy drugs. For most of these, there is no knowledge about side effects in healthy individuals, and no adequate doping tests. Therefore, anti-doping measures cannot rely solely on the continual improvement of doping analyses, but should include increased measures for doping prevention. Not only sports organizations, but also governmental agencies should be involved in developing and implementing these measures.

Effect of Sn doping on the room temperature magnetodielectric properties of yttrium iron garnet

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhizhi; Chen, Fu; Li, Junnan; Feng, Zekun; Nie, Yan, E-mail: nieyan@hust.edu.cn [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan (China)

2015-10-21

The structures, magnetic properties, permittivity spectra, and magnetodielectric (MD) effects of polycrystalline Y{sub 3}Fe{sub 5−x}Sn{sub x}O{sub 12} compounds prepared by solid state reactions were systematically investigated. The substitution of Sn{sup 4+} leads to lattice expansion and the donation of excess electrons in ceramics, which affects the concentration of Fe{sup 2+}, space charge, and electric dipole. As a result, as the amount of Sn dopant increases, so does saturation magnetization and permittivity in the low frequency band. The MD coefficient ([ε{sub r}(H) − ε{sub r}(0)]/ε{sub r}(0)) of lightly doped samples (x ≤ 0.05) is negative in the entire frequency band, reaching −2.3% at 350 MHz and 0.6 T for Y{sub 3}Fe{sub 4.95}Sn{sub 0.05}O{sub 12} ceramics. The MD coefficient of heavily doped samples (x > 0.05) is positive in the low frequency band, reaching 0.83% at 10 MHz and 0.6 T for Y{sub 3}Fe{sub 4.925}Sn{sub 0.075}O{sub 12} ceramics, and then decreasing with the increasing frequency, gradually becoming negative in the high frequency band. A detailed explanation is provided based on the origin of permittivity. This study provides a new methodology according to which the MD materials may be designed in order to satisfy the requirements of engineering applications.

Developing strategies for detection of gene doping.

Science.gov (United States)

Baoutina, Anna; Alexander, Ian E; Rasko, John E J; Emslie, Kerry R

2008-01-01

It is feared that the use of gene transfer technology to enhance athletic performance, the practice that has received the term 'gene doping', may soon become a real threat to the world of sport. As recognised by the anti-doping community, gene doping, like doping in any form, undermines principles of fair play in sport and most importantly, involves major health risks to athletes who partake in gene doping. One attraction of gene doping for such athletes and their entourage lies in the apparent difficulty of detecting its use. Since the realisation of the threat of gene doping to sport in 2001, the anti-doping community and scientists from different disciplines concerned with potential misuse of gene therapy technologies for performance enhancement have focused extensive efforts on developing robust methods for gene doping detection which could be used by the World Anti-Doping Agency to monitor athletes and would meet the requirements of a legally defensible test. Here we review the approaches and technologies which are being evaluated for the detection of gene doping, as well as for monitoring the efficacy of legitimate gene therapy, in relation to the detection target, the type of sample required for analysis and detection methods. We examine the accumulated knowledge on responses of the body, at both cellular and systemic levels, to gene transfer and evaluate strategies for gene doping detection based on current knowledge of gene technology, immunology, transcriptomics, proteomics, biochemistry and physiology. (c) 2008 John Wiley & Sons, Ltd.

Brief History of Anti-Doping.

Science.gov (United States)

Ljungqvist, Arne

2017-01-01

The fight against doping in sport as we know it today commenced by the creation of the International Olympic Committee (IOC) Medical Commission in 1961 following the death of a Danish cyclist during the Rome Olympic Games the year before. After a slow start, the fight got under way as from the early 1970s under the leadership of the IOC and of the International Association of Athletics Federations. Despite a lack of understanding and weak support even from the sports community, a series of measures were taken during the 1970s and 1980s which still form cornerstones of today's anti-doping strategy. In addition to information and education campaigns, the most important examples are the introduction of procedural rules for doping controls, the establishment and follow-up of a list of prohibited substances and methods, the accreditation of doping control laboratories, the introduction of in- and out-of-competition testing, rules for therapeutic use exemption, and the introduction of blood sampling. During the 1990s, the anti-doping fight gained increasing support both inside and outside the sport community. In order to harmonize the wide variety of rules that had developed both in sport organizations and at the domestic level and to promote anti-doping activities, the World Anti-Doping Agency (WADA) was jointly created by the Olympic movement and the public authorities in 1999. WADA is today carrying on the fight supported by the universally accepted WADA Code and an International Anti-Doping Convention under UNESCO. © 2017 S. Karger AG, Basel.

Superconductivity in doped two-leg ladder cuprates

International Nuclear Information System (INIS)

Qin Jihong; Yuan Feng; Feng Shiping

2006-01-01

Within the t-J ladder model, superconductivity with a modified d-wave symmetry in doped two-leg ladder cuprates is investigated based on the kinetic energy driven superconducting mechanism. It is shown that the spin-liquid ground-state at the half-filling evolves into the superconducting ground-state upon doping. In analogy to the doping dependence of the superconducting transition temperature in the planar cuprate superconductors, the superconducting transition temperature in doped two-leg ladder cuprates increases with increasing doping in the underdoped regime, and reaches a maximum in the optimal doping, then decreases in the overdoped regime

Hydrogen Solubility in Pr-doped and Un-doped YSZ for One Chamber Fuel Cell

DEFF Research Database (Denmark)

Bay, Lasse; Horita, T.; Sakai, N.

1998-01-01

SIMS analysis. Doping of Pr in the YSZ resulted in a higher intensity of the D ion, which indicated that hydrogen solubility was raised by the doping. The solubility of hydrogen in the electrolyte may affect the performance of one chamber fuel cells. (C) 1998 Elsevier Science B.V. All rights reserved.......Yttria-stabilised zirconia electrolytes (YSZ and Pr-doped YSZ) and yttria-doped strontium cerate (SYC) were tested in a one chamber fuel cell fed with a mixture of methane and air at 1223 K. The obtained performances were 4 mW cm(-2), 3 mW cm(-2), 2.5 mW cm(-2), and 0.15 mW cm(-2) for SYC, 1.8 mol...

High-efficiency silicon doping of InP and In0.53Ga0.47As in gas source and metalorganic molecular beam epitaxy using silicon tetrabromide

International Nuclear Information System (INIS)

Jackson, S.L.; Fresina, M.T.; Baker, J.E.; Stillman, G.E.

1994-01-01

Efficient vapor source Si doping of InP and In 0.53 Ga 0.47 As have been demonstrated using SiBr 4 as the Si source for both gas source (GSMBE) and metalorganic molecular beam epitaxy (MOMBE). Net electron concentrations ranging from n=2x10 17 to 6.8x10 19 cm -3 and from 9x10 16 to 3x10 19 cm -3 have been obtained for InP and In 0.53 Ga 0.47 As, respectively. Comparison of these data with those for Si 2 H 6 indicate that the Si incorporation efficiency with SiBr 4 is more than 10 000 times greater than with Si 2 H 6 for substrate temperatures in the range of 475≤T s ≤500 degree C. Specular surface morphologies were obtained, even for the most heavily doped samples. While [Si] as high as 1.8x10 20 cm -3 was obtained in InP, the net electron concentrations and 300 K Hall mobilities decrease with increasing [Si] for [Si]>6.8x10 19 cm -3 . Contact resistances as low as R c =3x10 -8 Ω cm 2 were obtained using a nonalloyed Ti/Pt/Au contact to InP layers doped to n=6.3x10 19 cm -3 . During GSMBE growth, an increased Si background concentration ([Si]∼2x10 17 cm -3 ) was observed after extended use of the SiBr 4 source for these heavy doping concentrations. This increased background was not observed in MOMBE-grown material. Depth profiles of pulse-doped structures indicate the absence of memory effects for structures grown by MOMBE

Transport properties for carbon chain sandwiched between heteroatom-doped carbon nanotubes with different doping sites

International Nuclear Information System (INIS)

Liu, Wenjiang; Deng, Xiaoqing; Cai, Shaohong

2016-01-01

The First-principles calculation is used to investigate the transport properties of a carbon chain connected with N-and/or B-doped caped carbon nanotube acting as electrodes. The I-V curves of the carbon chain are affected by the N/B doping sites, and rectifying behavior can be obtained distinctly when the carbon chain is just connected onto two doping atom sites (N- chain-B), and a weak rectification occurs when N (B) doping at other sites. Interestingly, the spin-filtering effects exist in the junction when it is doped at other sites, undoped system, or N-terminal carbon chains. However, no this behavior is found in N-chain-B and B-chain-B systems. The analysis on the transmission spectra, PDOS, LDOS, spin density, and the electron transmission pathways give an insight into the observed results for the system.

Transport properties for carbon chain sandwiched between heteroatom-doped carbon nanotubes with different doping sites

Energy Technology Data Exchange (ETDEWEB)

Liu, Wenjiang [Big Data and Information Engineering College of Guizhou University, Guiyang 550025 (China); Guizhou University of Finance and Economics, Guiyang 550025 (China); Deng, Xiaoqing, E-mail: xq-deng@163.com, E-mail: caish@mail.gufe.edu.cn [School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114 (China); Cai, Shaohong, E-mail: xq-deng@163.com, E-mail: caish@mail.gufe.edu.cn [Guizhou University of Finance and Economics, Guiyang 550025 (China)

2016-07-15

The First-principles calculation is used to investigate the transport properties of a carbon chain connected with N-and/or B-doped caped carbon nanotube acting as electrodes. The I-V curves of the carbon chain are affected by the N/B doping sites, and rectifying behavior can be obtained distinctly when the carbon chain is just connected onto two doping atom sites (N- chain-B), and a weak rectification occurs when N (B) doping at other sites. Interestingly, the spin-filtering effects exist in the junction when it is doped at other sites, undoped system, or N-terminal carbon chains. However, no this behavior is found in N-chain-B and B-chain-B systems. The analysis on the transmission spectra, PDOS, LDOS, spin density, and the electron transmission pathways give an insight into the observed results for the system.

Gene doping: of mice and men.

Science.gov (United States)

Azzazy, Hassan M E; Mansour, Mai M H; Christenson, Robert H

2009-04-01

Gene doping is the newest threat to the spirit of fair play in sports. Its concept stemmed out from legitimate gene therapy trials, but anti-doping authorities fear that they now may be facing a form of doping that is virtually undetectable and extremely appealing to athletes. This paper presents studies that generated mouse models with outstanding physical performance, by manipulating genes such as insulin-like growth factor 1 (IGF-1) or phosphoenolpyruvate carboxykinase (PEPCK), which are likely to be targeted for gene doping. The potential transition from super mice to super athletes will also be discussed, in addition to possible strategies for detection of gene doping.

Electrochemical n-doping of poly(dithienylvinylene). A comparison of cyclovoltammetric and conductive properties in n- and p-doping

Energy Technology Data Exchange (ETDEWEB)

Zotti, G. (Ist. di Polarografia ed Elettrochimica Preparative, Consiglio Nazionale delle Ricerche, Padua (Italy)); Schiavon, G. (Ist. di Polarografia ed Elettrochimica Preparative, Consiglio Nazionale delle Ricerche, Padua (Italy))

1994-03-15

Electrochemical n-doping of poly(dithienylvinylene) has been performed in AN+0.1 M N(C[sub n]H[sub 2n+1])[sub 4][sup +]ClO[sub 4][sup -] (n=1,2,3,4 and 6) and compared with p-doping. Cyclic voltammetry, in situ ESR and UV-Vis spectroelectrochemistry show that radical anions produced in n-doping are moderately unstable towards disproportionation whereas, in p-doping, radical cations are stabilized by [pi]-dimerization. In situ conductivity of n-doped polymer decreases as the size of the dopant cation increases, suggesting charge transport control by interchain hopping. The different conductivities of n- and p-doped polymers are due to the different sizes of the counterions. (orig.)

Ferromagnetism in doped or undoped spintronics nanomaterials

Science.gov (United States)

Qiang, You

2010-10-01

Much interest has been sparked by the discovery of ferromagnetism in a range of oxide doped and undoped semiconductors. The development of ferromagnetic oxide semiconductor materials with giant magnetoresistance (GMR) offers many advantages in spintronics devices for future miniaturization of computers. Among them, TM-doped ZnO is an extensively studied n-type wide-band-gap (3.36 eV) semiconductor with a tremendous interest as future mini-computer, blue light emitting, and solar cells. In this talk, Co-doped ZnO and Co-doped Cu2O semiconductor nanoclusters are successfully synthesized by a third generation sputtering-gas-aggregation cluster technique. The Co-doped nanoclusters are ferromagnetic with Curie temperature above room temperature. Both of Co-doped nanoclusters show positive magnetoresistance (PMR) at low temperature, but the amplitude of the PMRs shows an anomalous difference. For similar Co doping concentration at 5 K, PMR is greater than 800% for Co-doped ZnO but only 5% for Co-doped Cu2O nanoclusters. Giant PMR in Co-doped ZnO which is attributed to large Zeeman splitting effect has a linear dependence on applied magnetic field with very high sensitivity, which makes it convenient for the future spintronics applications. The small PMR in Co-doped Cu2O is related to its vanishing density of states at Fermi level. Undoped Zn/ZnO core-shell nanoparticle gives high ferromagnetic properties above room temperature due to the defect induced magnetization at the interface.

Fitness Doping and Body Management

DEFF Research Database (Denmark)

Thualagant, Nicole

This PhD thesis examines in a first paper the conceptualization of fitness doping and its current limitations. Based on a review of studies on bodywork and fitness doping it is emphasised that the definition of doping does not provide insights into bodywork of both men and women. Moreover......, it is argued that the social and a cultural context are missing in the many epidemiological studies on the prevalence of doping. The second paper explores the difficulties of implementing an anti-doping policy, which was originally formulated in an elite sport context, in a fitness context and more......-based fitness centres. Based on a survey in ten Danish club-based fitness centres and on narratives from semi-structured interviews, it is highlighted that the objectives of bodywork differ according to the users’ age and gender. Two different ways of investing in the body are explored in the paper, namely...

Dual Inhibition of EGFR and VEGF in Heavily Pretreated Patients with Metastatic Colorectal Cancer

DEFF Research Database (Denmark)

Larsen, Finn Ole; Markussen, Alice; Nielsen, Dorte

2017-01-01

: The combination of irinotecan, bevacizumab, and cetuximab/panitumumab is safe and shows a toxicity profile corresponding to what is expected from the agents alone. The results indicate that the combination in the 4th line may result in a high rate of disease control in heavily pretreated patients with metastatic...

Doping in elite sport – do the fans care? : public opinion on the consequences of doping scandals

OpenAIRE

Solberg, Harry Arne; Hanstad, Dag Vidar; Thøring, Thor Atle

2010-01-01

www.imrpublications.com There are indications that commercial stakeholders are reluctant to associate with sports involved in doping scandals. A survey of 925 Norwegian sports consumers supports this reluctance, showing no tolerance for pure doping substances. The majority were in favour of tough responses to athletes and sports involved in doping. Older respondents were more negative towards doping. Those who were strongly interested in sport were more willing than others to a...

A comparative study of semiconductor-based plasmonic metamaterials

DEFF Research Database (Denmark)

Naik, Gururaj V.; Boltasseva, Alexandra

2011-01-01

and very large negative real permittivity values, and in addition, their optical properties cannot be tuned. These issues that put severe constraints on the device applications of MMs could be overcome if semiconductors are used as plasmonic materials instead of metals. Heavily doped, wide bandgap oxide...... semiconductors could exhibit both a small negative real permittivity and relatively small losses in the NIR. Heavily doped oxides of zinc and indium were already reported to be good, low loss alternatives to metals in the NIR range. Here, we consider these transparent conducting oxides (TCOs) as alternative...

Nitrogen-doped graphene prepared by a transfer doping approach for the oxygen reduction reaction application

Science.gov (United States)

Mo, Zaiyong; Zheng, Ruiping; Peng, Hongliang; Liang, Huagen; Liao, Shijun

2014-01-01

Well defined nitrogen-doped graphene (NG) is prepared by a transfer doping approach, in which the graphene oxide (GO) is deoxidized and nitrogen doped by the vaporized polyaniline, and the GO is prepared by a thermal expansion method from graphite oxide. The content of doped nitrogen in the doped graphene is high up to 6.25 at% by the results of elements analysis, and oxygen content is lowered to 5.17 at%. As a non-precious metal cathode electrocatalyst, the NG catalyst exhibits excellent activity toward the oxygen reduction reaction, as well as excellent tolerance toward methanol. In 0.1 M KOH solution, its onset potential, half-wave potential and limiting current density for the oxygen reduction reaction reach 0.98 V (vs. RHE), 0.87 V (vs. RHE) and 5.38 mA cm-2, respectively, which are comparable to those of commercial 20 wt% Pt/C catalyst. The well defined graphene structure of the catalyst is revealed clearly by HRTEM and Raman spectra. It is suggested that the nitrogen-doping and large surface area of the NG sheets give the main contribution to the high ORR catalytic activity.

Room temperature ferromagnetism in Co doped ZnO within an optimal doping level of 5%

International Nuclear Information System (INIS)

Mohapatra, J.; Mishra, D.K.; Mishra, Debabrata; Perumal, A.; Medicherla, V.R.R.; Phase, D.M.; Singh, S.K.

2012-01-01

Highlights: ► Zn 1−x Co x O ((0 ≤ x ≤ 0.1)) system synthesized by solid state reaction technique. ► Observation of room temperature ferromagnetism for 3 and 5% Co doped ZnO. ► XPS and EPMA studies predict the occurrence of segregated CoO clusters. ► Suppresses ferromagnetic ordering in higher doping percentage of Co (>5%). -- Abstract: We report on the structural, micro-structural and magnetic properties of Zn 1−x Co x O (0 ≤ x ≤ 0.1) system. Electron probe micro-structural analysis on 5% Co doped ZnO indicates the presence of segregated cobalt oxide which is also confirmed from the Co 2p core level X-ray photoelectron spectrum. The presence of oxygen defects in lower percentage of Co doped ZnO (≤5%) enhances the carrier mediated exchange interaction and thereby enhancing the room-temperature ferromagnetic behaviour. Higher doping percentage of cobalt (>5%) creates weak link between the grains and suppresses the carrier mediated exchange interaction. This is the reason why room temperature ferromagnetism is not observed in 7% and 10% Co doped ZnO.

Functionalization of silicon-doped single walled carbon nanotubes at the doping site: An ab initio study

International Nuclear Information System (INIS)

Song Chen; Xia Yueyuan; Zhao Mingwen; Liu Xiangdong; Li Feng; Huang Boda; Zhang Hongyu; Zhang Bingyun

2006-01-01

We performed ab initio calculations on the cytosine-functionalized silicon-doped single walled carbon nanotubes (SWNT). The results show that silicon substitutional doping to SWNT can dramatically change the atomic and electronic structures of the SWNT. And more importantly, it may provide an efficient pathway for further sidewall functionalization to synthesize more complicated SWNT based complex materials, for example, our previously proposed base-functionalized SWNTs, because the doping silicon atom can improve the reaction activity of the tube at the doping site due to its preference to form sp3 hybridization bonding

Filament-induced luminescence and supercontinuum generation in undoped, Yb-doped, and Nd-doped YAG crystals

Science.gov (United States)

Kudarauskas, D.; Tamošauskas, G.; Vengris, M.; Dubietis, A.

2018-01-01

We present a comparative spectral study of filament-induced luminescence and supercontinuum generation in undoped, Yb-doped, and Nd-doped YAG crystals. We show that supercontinuum spectra generated by femtosecond filamentation in undoped and doped YAG crystals are essentially identical in terms of spectral extent. On the other hand, undoped and doped YAG crystals exhibit remarkably different filament-induced luminescence spectra whose qualitative features are independent of the excitation wavelength and provide information on the energy deposition to embedded dopants, impurities, and the crystal lattice itself. Our findings suggest that filament-induced luminescence may serve as a simple and non-destructive tool for spectroscopic studies in various transparent dielectric media.

[Doping in disabled sports. Doping control activities at the Paralympic Games 1984-2008 and in Germany 1992-2008].

Science.gov (United States)

Thevis, Mario; Hemmersbach, Peter; Geyer, Hans; Schänzer, Wilhelm

2009-12-15

Activities concerning the fight against doping with regard to the Paralympic Games have been initiated in 1984, when first doping controls were conducted. The foundation of the International Paralympic Committee exactly 20 years ago (1989) considerably supported systematic sports drug-testing programs specifically designed to meet the particular challenges related to disabled sports, which yielded a variety of adverse analytical findings (e.g., with anabolic steroids, diuretics, corticosteroids, and stimulants) especially at Paralympic Summer Games. In Germany, doping controls for handicapped athletes were established in 1992 and have been conducted since by the National Paralympic Committee Germany and the National Anti-Doping Agency. Also here, various analogies in terms of antidoping rule violations were found in comparison to doping controls of nondisabled athletes. In the present article, available numbers of samples analyzed at Paralympic Summer and Winter Games as well as within the doping control program for disabled sports in Germany are summarized, and particularities concerning sample collection and the doping method termed boosting are presented.

Growth of misfit dislocation-free p/p+ thick epitaxial silicon wafers on Ge-B-codoped substrates

International Nuclear Information System (INIS)

Jiang Huihua; Yang Deren; Ma Xiangyang; Tian Daxi; Li Liben; Que Duanlin

2006-01-01

The growth of p/p + silicon epitaxial silicon wafers (epi-wafers) without misfit dislocations has been successfully achieved by using heavily boron-doped Czochralski (CZ) silicon wafers codoped with desirable level of germanium as the substrates. The lattice compensation by codoping of germanium and boron into the silicon matrix to reduce the lattice mismatch between the substrate (heavily boron-doped) and epi-layer (lightly boron-doped) is the basic idea underlying in the present achievement. In principle, the codoping of germanium and boron in the CZ silicon can be tailored to achieve misfit dislocation-free epi-layer with required thickness. It is reasonably expected that the presented solution to elimination of misfit dislocations in the p/p + silicon wafers can be applied in the volume production

Gene doping: possibilities and practicalities.

Science.gov (United States)

Wells, Dominic J

2009-01-01

Our ever-increasing understanding of the genetic control of cardiovascular and musculoskeletal function together with recent technical improvements in genetic manipulation generates mounting concern over the possibility of such technology being abused by athletes in their quest for improved performance. Genetic manipulation in the context of athletic performance is commonly referred to as gene doping. A review of the literature was performed to identify the genes and methodologies most likely to be used for gene doping and the technologies that might be used to identify such doping. A large number of candidate performance-enhancing genes have been identified from animal studies, many of them using transgenic mice. Only a limited number have been shown to be effective following gene transfer into adults. Those that seem most likely to be abused are genes that exert their effects locally and leave little, if any, trace in blood or urine. There is currently no evidence that gene doping has yet been undertaken in competitive athletes but the anti-doping authorities will need to remain vigilant in reviewing this rapidly emerging technology. The detection of gene doping involves some different challenges from other agents and a number of promising approaches are currently being explored. 2009 S. Karger AG, Basel

Doping of ZnO nanowires using phosphorus diffusion from a spin-on doped glass source

International Nuclear Information System (INIS)

Bocheux, A.; Robin, I. C.; Bonaimé, J.; Hyot, B.; Feuillet, G.; Kolobov, A. V.; Fons, P.; Mitrofanov, K. V.; Tominaga, J.; Tamenori, Y.

2014-01-01

In this article, we report on ZnO nanowires that were phosphorus doped using a spin on dopant glass deposition and diffusion method. Photoluminescence measurements suggest that this process yields p-doped ZnO. The spatial location of P atoms was studied using x-ray near-edge absorption structure spectroscopy and it is concluded that the doping is amphoteric with P atoms located on both Zn and O sites

Neutron transmutation doping of polycrystalline silicon

International Nuclear Information System (INIS)

Cleland, J.W.; Westbrook, R.D.; Wood, R.F.; Young, R.T.

1976-04-01

Chemical vapor deposition (CVD) of doped silane has been used by others to deposit a polycrytalline silicon film (polysil) on metal or graphite substrates, but dopant migration to grain boundaries during deposition apparently prohibits attaining a uniform or desired dopant concentration. In contrast, we have used neutron transmutation doping to introduce a uniform phosphorus dopant concentration in commercially available undoped CVD polysil at doping concentrations greater than or equal to 2 x 10 15 cm -3 . Radiation damage annealing to 800 0 C did not indicate dopant migration. Carrier mobility increased with doping concentration and the minority carrier lifetime (MCL) appears to be comparable to that of neutron transmutation doped (NTD) single crystal Si. Application of this technique to photovoltaic solar cell fabrication is discussed

Probing the doping mechanisms and electrical properties of Al, Ga and In doped ZnO prepared by spray pyrolysis

KAUST Repository

Maller, Robert

2016-05-24

The measured structural, optical and electrical properties of Al, Ga and In doped ZnO films deposited using spray pyrolysis are reported over the doping range 0.1 - 3 atomic percent (at. %). Over the entire doping series highly transparent, polycrystalline thin films are prepared. Using the AC Hall effect we probe the electronic properties of our doped films separating the impact of doping on the measured charge carrier concentrations and Hall mobility, with an emphasis on the low doping, < 1 at. %, range. In this doping range highly resistive films are formed and we highlight AC Hall as a reliable and highly reproducible technique for analysing the doping mechanism. The implementation of a simple, post-deposition heat treatment of our AZO films creates typical films with charge carrier concentrations exceeding > 1019 cm-3 and electron mobilities over 10 cm2/Vs. We describe in detail the nature of the defect chemistry and the role of intrinsic defects, particularly traps, and show that despite significant variations in dopant species and grain boundary concentrations that the defect chemistry dominates the electrical characteristics.

Probing the doping mechanisms and electrical properties of Al, Ga and In doped ZnO prepared by spray pyrolysis

KAUST Repository

Maller, Robert; Porte, Yoann; Alshareef, Husam N.; McLachlan, Martyn

2016-01-01

The measured structural, optical and electrical properties of Al, Ga and In doped ZnO films deposited using spray pyrolysis are reported over the doping range 0.1 - 3 atomic percent (at. %). Over the entire doping series highly transparent, polycrystalline thin films are prepared. Using the AC Hall effect we probe the electronic properties of our doped films separating the impact of doping on the measured charge carrier concentrations and Hall mobility, with an emphasis on the low doping, < 1 at. %, range. In this doping range highly resistive films are formed and we highlight AC Hall as a reliable and highly reproducible technique for analysing the doping mechanism. The implementation of a simple, post-deposition heat treatment of our AZO films creates typical films with charge carrier concentrations exceeding > 1019 cm-3 and electron mobilities over 10 cm2/Vs. We describe in detail the nature of the defect chemistry and the role of intrinsic defects, particularly traps, and show that despite significant variations in dopant species and grain boundary concentrations that the defect chemistry dominates the electrical characteristics.

Inside athletes' minds: Preliminary results from a pilot study on mental representation of doping and potential implications for anti-doping

Directory of Open Access Journals (Sweden)

Mazanov Jason

2011-05-01

Full Text Available Abstract Background Despite the growing body of literature and putative links between the use of ergogenic nutritional supplements, doping and illicit drugs, it remains unclear whether, in athletes' minds, doping aligns with illicit behaviour or with functional use of chemical or natural preparations. To date, no attempt has been made to quantitatively explore athletes' mental representation of doping in relation to illegality and functionality. Methods A convenience sample of student athletes from a large South-Eastern Australian university responded to an on-line survey. Competitive athletes (n = 46 were grouped based on self-reported use as follows: i none used (30%, ii supplement only (22%, iii illicit only (26% and iv both supplements and illicit drug use (22%. Whereas no athlete reported doping, data provided on projected supplement-, doping- and drug use by the four user groups allowed evaluation of doping-related cognition in the context of self-reported supplement- and illicit drug taking behaviour; and comparison between these substances. Results A significantly higher prevalence estimation was found for illicit drug use and a trend towards a biased social projection emerged for supplement use. Doping estimates by user groups showed mixed results, suggesting that doping had more in common with the ergogenic nutritional supplement domain than the illicit drug domain. Conclusions Assessing the behavioural domain to which doping belongs to in athletes' mind would greatly advance doping behaviour research toward prevention and intervention. Further investigation refining the peculiarity of the mental representation of doping with a larger study sample, controlling for knowledge of doping and other factors, is warranted.

Alternative medicine and doping in sports

Directory of Open Access Journals (Sweden)

Benjamin Koh

2012-01-01

Full Text Available Athletes are high achievers who may seek creative or unconventional methods to improve performance. The literature indicates that athletes are among the heaviest users of complementary and alternative medicine (CAM and thus may pioneer population trends in CAM use. Unlike non-athletes, athletes may use CAM not just for prevention, treatment or rehabilitation from illness or injuries, but also for performance enhancement. Assuming that athletes’ creative use of anything unconventional is aimed at “legally” improving performance, CAM may be used because it is perceived as more “natural” and erroneously assumed as not potentially doping. This failure to recognise CAMs as pharmacological agents puts athletes at risk of inadvertent doping.The general position of the World Anti-Doping Authority (WADA is one of strict liability, an application of the legal proposition that ignorance is no excuse and the ultimate responsibility is on the athlete to ensure at all times whatever is swallowed, injected or applied to the athlete is both safe and legal for use. This means that a violation occurs whether or not the athlete intentionally or unintentionally, knowingly or unknowingly, used a prohibited substance/method or was negligent or otherwise at fault. Athletes are therefore expected to understand not only what is prohibited, but also what might potentially cause an inadvertent doping violation. Yet, as will be discussed, athlete knowledge on doping is deficient and WADA itself sometimes changes its position on prohibited methods or substances. The situation is further confounded by the conflicting stance of anti-doping experts in the media. These highly publicised disagreements may further portray inconsistencies in anti-doping guidelines and suggest to athletes that what is considered doping is dependent on the dominant political zeitgeist. Taken together, athletes may believe that unless a specific and explicit ruling is made, guidelines are

Alternative medicine and doping in sports.

Science.gov (United States)

Koh, Benjamin; Freeman, Lynne; Zaslawski, Christopher

2012-01-01

Athletes are high achievers who may seek creative or unconventional methods to improve performance. The literature indicates that athletes are among the heaviest users of complementary and alternative medicine (CAM) and thus may pioneer population trends in CAM use. Unlike non-athletes, athletes may use CAM not just for prevention, treatment or rehabilitation from illness or injuries, but also for performance enhancement. Assuming that athletes' creative use of anything unconventional is aimed at "legally" improving performance, CAM may be used because it is perceived as more "natural" and erroneously assumed as not potentially doping. This failure to recognise CAMs as pharmacological agents puts athletes at risk of inadvertent doping.The general position of the World Anti-Doping Authority (WADA) is one of strict liability, an application of the legal proposition that ignorance is no excuse and the ultimate responsibility is on the athlete to ensure at all times whatever is swallowed, injected or applied to the athlete is both safe and legal for use. This means that a violation occurs whether or not the athlete intentionally or unintentionally, knowingly or unknowingly, used a prohibited substance/method or was negligent or otherwise at fault. Athletes are therefore expected to understand not only what is prohibited, but also what might potentially cause an inadvertent doping violation. Yet, as will be discussed, athlete knowledge on doping is deficient and WADA itself sometimes changes its position on prohibited methods or substances. The situation is further confounded by the conflicting stance of anti-doping experts in the media. These highly publicised disagreements may further portray inconsistencies in anti-doping guidelines and suggest to athletes that what is considered doping is dependent on the dominant political zeitgeist. Taken together, athletes may believe that unless a specific and explicit ruling is made, guidelines are open to interpretation

Ductility of Mo–12Si–8.5B alloys doped with lanthanum oxide by the liquid–liquid doping method

Energy Technology Data Exchange (ETDEWEB)

Li, Wenhu [School of Materials Science & Engineering, Xi’an University of Technology, Xi’an 710048 (China); School of Materials Science & Engineering, Shaanxi University of Technology, Hanzhong 723000 (China); Zhang, Guojun, E-mail: zhangguojun@xaut.edu.cn [School of Materials Science & Engineering, Xi’an University of Technology, Xi’an 710048 (China); Wang, Shixiong [School of Materials Science & Engineering, Xi’an University of Technology, Xi’an 710048 (China); Li, Bin; Sun, Jun [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China)

2015-09-05

Highlights: • Alloys doping lanthanum oxide by L–L doped method were prepared by hot pressing. • The compression strength of alloys are superior. • The fracture toughness of alloys is improved by L–L doped method. - Abstract: Mo–12Si–8.5B (Mo–Si–B) alloys doped with different mass fractions (0.3 wt%, 0.6 wt%, and 0.9 wt%) of lanthanum oxide (La{sub 2}O{sub 3}) were prepared by liquid–liquid (L–L) doping, mechanical alloying and hot pressing sintering techniques. The observation of the microstructures of the Mo–Si–B alloys reveals that the grain sizes of the alloys were refined with the increase in La{sub 2}O{sub 3} doping. The fracture toughness values of the alloys of over 10 MPa m{sup 1/2} reveal that the addition of La{sub 2}O{sub 3} via the L–L doping method can obviously improve the alloy fracture toughness compared to the alloys doped with La{sub 2}O{sub 3} via the solid–solid (S–S) doping method. In addition, compression tests indicate that the compression strength of the alloys was improved compared to Mo–12Si–8.5B alloys.

[Current status and prospects of gene doping detection].

Science.gov (United States)

Wang, Wenjun; Zhang, Sichun; Xu, Jingjuan; Xia, Xinghua; Tian, Yaping; Zhang, Xinrong; Chen, Hong-Yuan

2008-07-01

The fast development of biotechnology promotes the development of doping. From recombinant protein to gene doping, there is a great challenge to their detection. The improvement of gene therapy and potential to enhance athletic performance open the door for gene doping. After a brief introduction of the concept of gene doping, the current status and prospects of gene doping detection are reviewed.

[Advances and strategies in gene doping detection].

Science.gov (United States)

He, Jiangang; Liu, Zhen; Liu, Jing; Dou, Peng; Chen, Hong-Yuan

2008-07-01

This review surveys the recent status of gene doping detection and the strategies for anti-gene doping. The main gene doping candidates for athletes are summarized, and the advances in the detection of the proteins expressed by these genes such as erythropoietin (EPO) and human growth hormone (hGH) are reviewed. The potential detection strategies for further gene doping analysis are also discussed.

Doping characteristics of Si-doped n-GaN Epilayers grown by low-pressure metal-organic chemical-vapor deposition

CERN Document Server

Noh, S K; Park, S E; Lee, I H; Choi, I H; Son, S J; Lim, K Y; Lee, H J

1998-01-01

We studied doping behaviors through analysis of the electronic properties of a series of undoped and Si-doped GaN epilayers grown on (0001) sapphire substrates by the low-pressure metal-organic chemical-vapor deposition (LP-MOCVD) technique. The doping efficiency was in the range of 0.4 - 0.8, and an empirical relation expressed as eta = 0.45 log[Si] - 8.1 was obtained. The temperature dependence of carrier concentration showed that the donor activation energy monotonically decreased from 17.6 meV to almost zero as the doping level increased. We suggest that the reduction in the activation energy is related not to autodoped defect centers but to doped Si donors and that the behavior originates from the formation of an impurity band. On the basis of an abrupt change in the compensation ratio from 0.9 to 0.5 by Si-doping, an exceptional difference in the Hall mobility between the undoped and the Si-doped films is explained by a mixed conduction mechanism of electrons and holes.

The EVEREST Doping Profile Module. Version 4

International Nuclear Information System (INIS)

Ashby, J.; Fowler, R.; Greenough, C.

1998-01-01

In this report we describe the EVEREST Doping Module which forms part of the EVEREST suite of programs. The doping module is responsible for generating a neutral file which gives the acceptor and donor densities at each node the device mesh. The neutral file also contains details of the functions used to generate the doping as mesh refinement in the solver requires this. Commands allow the definition of background doping, regions of uniform doping, non-uniform doping relating to windows found in the Geometry neutral file and a user-programmable FORTRAN subroutine which computes doping concentrations as a function of position. The EVEREST suite is one of the products of the ESPRIT project EVEREST (ESPRIT 962E-17, Three-Dimensional Algorithms for a Robust and Efficient Semiconductor Simulator with Parameter Extraction). EVEREST was a four-year project supported by the European Community under the European Strategic Program for Research in Information Technology (ESPRIT) which is investigating suitable algorithms for the analysis of semiconductor devices in three dimensions, and developing software implementing the most effective of those algorithms. The original authors of the Doping Module were G.A. Duffett and M.S. Towers of University College, Swansea. (author)

Diffusivity-mobility relationship for heavily doped semiconductors exhibiting band tails

International Nuclear Information System (INIS)

Khan, Arif; Das, Atanu

2010-01-01

A relationship between the mobility and diffusivity of semiconductors exhibiting band tails has been presented. The relationship is general enough to be applicable to both non-degenerate and degenerate semiconductors, and to semiconductors with and without band tails. It is suitable for studying electrical transport in these semiconductors.

Becoming a Heavily Tattooed Young Body: From a Bodily Experience to a Body Project

Science.gov (United States)

Ferreira, Vitor Sérgio

2014-01-01

Why some young people start to tattoo their bodies? And why some of them keep going on with this practice, until having all body tattooed? What doing so means to them? These are some of the questions that underlie a qualitative research project carried out in Portugal on heavily tattooed young people. In this article, the author discusses their…

[Doping, sport and addiction--any links?].

Science.gov (United States)

Foucart, J; Verbanck, P; Lebrun, P

2015-01-01

Sport is widely encouraged as it is beneficial for health. However, high-performance sport is more and more associated to rather suspicious practices; doping is one of the best example. From a physician point of view, the use of doping agents is obviously a major concern because taking such products often induce serious adverse effects on health. The present manuscript aims to inform physicians about the most frequent doping practices. It also points out that intensive sport can generate an "addictive" behavior sharing with "common"addictions a loss of practice control, a lack of interest in other activities and even a sport's practice detrimental to athlete's health. Analysis of the doping issue needs to take this reality into account as some doping products display an established " addictive" effect.

Doping properties of cadmium-rich arsenic-doped CdTe single crystals: Evidence of metastable AX behavior

Science.gov (United States)

Nagaoka, Akira; Kuciauskas, Darius; Scarpulla, Michael A.

2017-12-01

Cd-rich composition and group-V element doping are of interest for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe, but the critical details concerning point defects are not yet fully established. Herein, we report on the properties of arsenic doped CdTe single crystals grown from Cd solvent by the travelling heater method. The photoluminescence spectra and activation energy of 74 ± 2 meV derived from the temperature-dependent Hall effect are consistent with AsTe as the dominant acceptor. Doping in the 1016 to 1017/cm3 range is achieved for measured As concentrations between 1016 and 1020/cm3 with the highest doping efficiency of 40% occurring near 1017 As/cm3. We observe persistent photoconductivity, a hallmark of light-induced metastable configuration changes consistent with AX behavior. Additionally, quenching experiments reveal at least two mechanisms of increased p-type doping in the dark, one decaying over 2-3 weeks and the other persisting for at least 2 months. These results provide essential insights for the application of As-doped CdTe in thin film solar cells.

Formation of hydroxyl radicals and kinetic study of 2-chlorophenol photocatalytic oxidation using C-doped TiO2, N-doped TiO2, and C,N Co-doped TiO2 under visible light.

Science.gov (United States)

Ananpattarachai, Jirapat; Seraphin, Supapan; Kajitvichyanukul, Puangrat

2016-02-01

This work reports on synthesis, characterization, adsorption ability, formation rate of hydroxyl radicals (OH(•)), photocatalytic oxidation kinetics, and mineralization ability of C-doped titanium dioxide (TiO2), N-doped TiO2, and C,N co-doped TiO2 prepared by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy were used to analyze the titania. The rate of formation of OH(•) for each type of titania was determined, and the OH-index was calculated. The kinetics of as-synthesized TiO2 catalysts in photocatalytic oxidation of 2-chlorophenol (2-CP) under visible light irradiation were evaluated. Results revealed that nitrogen was incorporated into the lattice of titania with the structure of O-Ti-N linkages in N-doped TiO2 and C,N co-doped TiO2. Carbon was joined to the Ti-O-C bond in the C-doped TiO2 and C,N co-doped TiO2. The 2-CP adsorption ability of C,N co-doped TiO2 and C-doped TiO2 originated from a layer composed of a complex carbonaceous mixture at the surface of TiO2. C,N co-doped TiO2 had highest formation rate of OH(•) and photocatalytic activity due to a synergistic effect of carbon and nitrogen co-doping. The order of photocatalytic activity per unit surface area was the same as that of the formation rate of OH(•) unit surface area in the following order: C,N co-doped TiO2 > C-doped TiO2 > N-doped TiO2 > undoped TiO2.

Optical properties of highly n-doped germanium obtained by in situ doping and laser annealing

Science.gov (United States)

Frigerio, J.; Ballabio, A.; Gallacher, K.; Giliberti, V.; Baldassarre, L.; Millar, R.; Milazzo, R.; Maiolo, L.; Minotti, A.; Bottegoni, F.; Biagioni, P.; Paul, D.; Ortolani, M.; Pecora, A.; Napolitani, E.; Isella, G.

2017-11-01

High n-type doping in germanium is essential for many electronic and optoelectronic applications especially for high performance Ohmic contacts, lasing and mid-infrared plasmonics. We report on the combination of in situ doping and excimer laser annealing to improve the activation of phosphorous in germanium. An activated n-doping concentration of 8.8  ×  1019 cm-3 has been achieved starting from an incorporated phosphorous concentration of 1.1  ×  1020 cm-3. Infrared reflectivity data fitted with a multi-layer Drude model indicate good uniformity over a 350 nm thick layer. Photoluminescence demonstrates clear bandgap narrowing and an increased ratio of direct to indirect bandgap emission confirming the high doping densities achieved.

In-situ doped junctionless polysilicon nanowires field effect transistors for low-cost biosensors

DEFF Research Database (Denmark)

Zulfiqar, Azeem; Patou, François; Pfreundt, Andrea

2017-01-01

by sweeping the back gate voltage while keeping the source drain potential to a constant value and surface characterization is done by applying liquid gate in phosphate buffered saline (PBS) solution. The fabricated SiNWs sensors functionalized with (3-aminopropyl)triethoxysilane (APTES) have demonstrated...

Intended or Unintended Doping? A Review of the Presence of Doping Substances in Dietary Supplements Used in Sports.

Science.gov (United States)

Martínez-Sanz, José Miguel; Sospedra, Isabel; Ortiz, Christian Mañas; Baladía, Eduard; Gil-Izquierdo, Angel; Ortiz-Moncada, Rocio

2017-10-04

The use of dietary supplements is increasing among athletes, year after year. Related to the high rates of use, unintentional doping occurs. Unintentional doping refers to positive anti-doping tests due to the use of any supplement containing unlisted substances banned by anti-doping regulations and organizations, such as the World Anti-Doping Agency (WADA). The objective of this review is to summarize the presence of unlabeled doping substances in dietary supplements that are used in sports. A review of substances/metabolites/markers banned by WADA in ergonutritional supplements was completed using PubMed. The inclusion criteria were studies published up until September 2017, which analyzed the content of substances, metabolites and markers banned by WADA. 446 studies were identified, 23 of which fulfilled all the inclusion criteria. In most of the studies, the purpose was to identify doping substances in dietary supplements. Substances prohibited by WADA were found in most of the supplements analyzed in this review. Some of them were prohormones and/or stimulants. With rates of contamination between 12 and 58%, non-intentional doping is a point to take into account before establishing a supplementation program. Athletes and coaches must be aware of the problems related to the use of any contaminated supplement and should pay special attention before choosing a supplement, informing themselves fully and confirming the guarantees offered by the supplement.

Preparation and properties of yttria doped tetragonal zirconia polycrystal/Sr-doped barium hexaferrite ceramic composites

International Nuclear Information System (INIS)

Wang, Shanshan; Zhang, Chao; Guo, Ruisong; Liu, Lan; Yang, Yuexia; Li, Kehang

2015-01-01

Highlights: • The 3Y-TZP/Sr-doped barium ferrite composites were prepared. • The saturation magnetization was improved by 15% with Sr-doping. • The dispersion coefficient p could reflect the microscopic lattice variation. • The composite with x = 0.5 had the maximum fracture toughness of 8.3 MPa m 1/2 . - Abstract: The effects of substitution of Ba 2+ by Sr 2+ on the magnetic property of barium ferrite and addition barium ferrite secondary phase to the 3 mol% yttria-doped tetragonal zirconia polycrystal (3Y-TZP) matrix on the mechanical property of composites were investigated. The Sr-doped barium ferrite (Ba 1−x Sr x Fe 12 O 19 , x = 0, 0.25, 0.50 and 0.75) was synthesized by solid-state reaction in advance. Then 3Y-TZP/20 wt% Sr-doped barium ferrite composites were prepared by means of conventional ceramic method. It was found that a moderate amount of Sr added to barium ferrite could boost the saturation magnetization by 15% compared with the composites without Sr-doping. Besides, the composite with x = 0.50 possessed the best mechanical properties, such as 11.5 GPa for Vickers hardness and 8.3 MPa m 1/2 for fracture toughness, respectively. It was demonstrated that magnetic and mechanical properties of the composites could be harmonized by the incorporation of barium ferrite secondary phase

Cytogenetic abnormalities of the descendants of permanent residents of heavily contaminated East Kazakhstan.

Science.gov (United States)

Chaizhunusova, Nailya; Madiyeva, Madina; Tanaka, Kimio; Hoshi, Masaharu; Kawano, Noriyuki; Noso, Yoshihiro; Takeichi, Nobuo; Rakhypbekov, Tolebay; Urazalina, Nailya; Dovgal, Galina; Rymbaeva, Tamara; Tokanova, Sholpan; Beisengazina, Meruert; Kembayeva, Kulypash; Inoue, Ken

2017-11-01

More than 400 nuclear explosion tests were conducted at the Semipalatinsk Nuclear Test Site (SNTS) and significant radioactive substances were released. The long-term consequences of the activities at the SNTS and the appearance of any hereditary effects remain insufficiently studied about 25 years after the test site was closed. The population living in villages near the SNTS are considered to have been heavily exposed to external and internal radiation. This study aims to perform an assessment and comprehensive cytogenetic analysis of the inhabitants living near the SNTS, and their first-(F1) and second-(F2) generation children. Residents of the East Kazakhstan region living in the area covered by the former SNTS were included in the study. To evaluate the hereditary effects of nuclear testing, comprehensive chromosome analyses were performed in lymphocytes using conventional Giemsa and fluorescent in situ hybridization methods in 115 F1 and F2 descendants in the villages of Dolon and Sarzhal, which were heavily contaminated. The parents of the subjects had permanently lived in the villages. A higher number of stable-type chromosome aberrations such as translocations was found in these residents than in 80 residents of the control area, Kokpecty, which indicates the possibility that radiation had biological effects on the exposed subjects.

Heteroatom doped graphene in photocatalysis: A review

International Nuclear Information System (INIS)

Putri, Lutfi Kurnianditia; Ong, Wee-Jun; Chang, Wei Sea; Chai, Siang-Piao

2015-01-01

Graphical abstract: - Highlights: • Doping graphene with foreign atoms extends its function in the photocatalyst system. • Chemically doped graphene improved the electrical conductivity. • Chemically doped graphene outperform conventional rGO as a semiconductor support. • Chemically doped graphene cause bandgap opening and formation of catalytic sites. • Chemically doped graphene can behave as functional standalone photocatalyst. - Abstract: Photocatalysis has been a focus of great attention due to its useful environmental applications such as eliminating hazardous pollutants and generating sustainable energy. Coincidentally, graphene, a 2D allotrope of carbon, has also infiltrated many research fields due to its outstanding properties – photocatalysis being no exception. As of recent, there has been growing research focus on heteroatom (O, N, B, P and S) doping of graphene and its emergent application opportunities. In this study, rather than the familiar graphene as the electron transfer medium that is normally integrated in a photocatalyst system, we contrarily explore the implication of heteroatom doped graphene and the underlying mechanism behind their advantageous uses in photocatalysis. This review surveys the literature and highlights recent progress and challenges in the development of chemically doped graphene in the photocatalysis scene. It is desired that this review will promote awareness and encourage further investigations for the development in this budding research area.

A novel approach for the improvement of electrostatic behaviour of physically doped TFET using plasma formation and shortening of gate electrode with hetero-gate dielectric

Science.gov (United States)

Soni, Deepak; Sharma, Dheeraj; Aslam, Mohd.; Yadav, Shivendra

2018-04-01

This article presents a new device configuration to enhance current drivability and suppress negative conduction (ambipolar conduction) with improved RF characteristics of physically doped TFET. Here, we used a new approach to get excellent electrical characteristics of hetero-dielectric short gate source electrode TFET (HD-SG SE-TFET) by depositing a metal electrode of 5.93 eV work function over the heavily doped source (P+) region. Deposition of metal electrode induces the plasma (thin layer) of holes under the Si/HfO2 interface due to work function difference of metal and semiconductor. Plasma layer of holes is advantageous to increase abruptness as well as decrease the tunneling barrier at source/channel junction for attaining higher tunneling rate of charge carriers (i.e., electrons), which turns into 86.66 times higher ON-state current compared with the conventional physically doped TFET (C-TFET). Along with metal electrode deposition, gate electrode is under-lapped for inducing asymmetrical concentration of charge carriers in the channel region, which is helpful for widening the tunneling barrier width at the drain/channel interface. Consequently, HD-SG SE-TFET shows suppression of ambipolar behavior with reduction in gate-to-drain capacitance which is beneficial for improvement in RF performance. Furthermore, the effectiveness of hetero-gate dielectric concept has been used for improving the RF performance. Furthermore, reliability of C-TFET and proposed structures has been confirmed in term of linearity.

DFT study of Al doped armchair SWCNTs

Energy Technology Data Exchange (ETDEWEB)

Dhiman, Shobhna, E-mail: s-dhiman@hotmail.com [Department of Applied Science, PEC, University of Technology, Chandigarh -160012 (India); Rani, Anita [Guru Nanak College for Girls, Sri Muktsar Sahib, Punjab-152026 (India); Kumar, Ranjan; Dharamvir, Keya [Department of Physics, Panjab University, Chandigarh-160014 (India)

2016-05-23

Electronic properties of endohedrally doped armchair single-walled carbon nanotubes (SWCNTs) with a chain of six Al atoms have been studied using ab-initio density functional theory. We investigate the binding energy/atom, ionization potential, electron Affinity and Homo-Lumo gap of doped armchair SWNTs from (4,4) to (6,6) with two ends open. BE/dopant atom and ionization potential is maximum for (6, 6) doped armchair carbon nanotube; suggest that it is more stable than (4, 4) and (5, 5) doped tubes. HOMO - LUMO gap of Al doped arm chair carbon nanotubes decreases linearly with the increase in diameter of the tube. This shows that confinement induce a strong effect on electronic properties of doped tubes. These combined systems can be used for future nano electronics. The ab–initio calculations were performed with SIESTA code using generalized gradient approximation (GGA).

Optical and magneto-optical properties of the electron-doped and hole-doped C{sub 82} crystal

Energy Technology Data Exchange (ETDEWEB)

Rostampour, E., E-mail: el_rostampour@yahoo.com [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Koohi, A. [Plasma Physics and Nuclear Fusion Research School, Nuclear Science and Technology Research Institute, AEOI, Tehran (Iran, Islamic Republic of)

2015-01-15

The optical and magnetic properties of the doped C{sub 82} crystal have been investigated by Su–Schrieffer–Heeger (SSH) model, which is based on the Ewald method. When the C{sub 82} molecule is doped with one electron (or hole), a single electron is remained in the energy level that affects the optical and magnetic properties of the C{sub 82} crystal. The lattice and electronic structures of C{sub 82} changed with doping electron (or hole) in the molecule of C{sub 82}. Therefore, polarons are predicted in doped fullerenes. The obtained results showed that the dielectric tensor of the C{sub 82} crystal increased with doping electron (or hole) in the molecule of C{sub 82}. The spectral shapes of the dielectric tensor, circular dichroism and birefringence coefficient of the C{sub 82} crystal turn out to be determined mainly by the geometrical distributions of the pentagons in the fullerene structures.

Doping dependence of magnetic and transport properties in single crystalline Co-doped BaFe2As2

International Nuclear Information System (INIS)

Nakajima, Yasuyuki; Taen, Toshihiro; Tamegai, Tsuyoshi

2010-01-01

We report the doping dependence of transport and magnetic properties in Co-doped BaFe 2 As 2 . With increasing Co concentration x, structural and magnetic transitions are suppressed and superconductivity emerges in the range of 0.3 c at low temperatures and low fields obtained from bulk magnetization is reasonably large and the doping dependence shows a maximum at x∼0.07 similar to T c . The values of J c at low temperatures reach about 1x10 6 A/cm 2 around the optimally doped region, which is potentially attractive for technological applications.

Optical properties of highly n-doped germanium obtained by in situ doping and laser annealing

International Nuclear Information System (INIS)

Frigerio, J; Ballabio, A; Isella, G; Gallacher, K; Millar, R; Paul, D; Gilberti, V; Baldassarre, L; Ortolani, M; Milazzo, R; Napolitani, E; Maiolo, L; Minotti, A; Pecora, A; Bottegoni, F; Biagioni, P

2017-01-01

High n-type doping in germanium is essential for many electronic and optoelectronic applications especially for high performance Ohmic contacts, lasing and mid-infrared plasmonics. We report on the combination of in situ doping and excimer laser annealing to improve the activation of phosphorous in germanium. An activated n-doping concentration of 8.8  ×  10 19 cm −3 has been achieved starting from an incorporated phosphorous concentration of 1.1  ×  10 20 cm −3 . Infrared reflectivity data fitted with a multi-layer Drude model indicate good uniformity over a 350 nm thick layer. Photoluminescence demonstrates clear bandgap narrowing and an increased ratio of direct to indirect bandgap emission confirming the high doping densities achieved. (paper)

IR-doped ruthenium oxide catalyst for oxygen evolution

Science.gov (United States)

Valdez, Thomas I. (Inventor); Narayanan, Sekharipuram R. (Inventor)

2012-01-01

A method for preparing a metal-doped ruthenium oxide material by heating a mixture of a doping metal and a source of ruthenium under an inert atmosphere. In some embodiments, the doping metal is in the form of iridium black or lead powder, and the source of ruthenium is a powdered ruthenium oxide. An iridium-doped or lead-doped ruthenium oxide material can perform as an oxygen evolution catalyst and can be fabricated into electrodes for electrolysis cells.

Electronic Raman response in electron-doped cuprate superconductors

International Nuclear Information System (INIS)

Geng Zhihao; Feng Shiping

2012-01-01

The electronic Raman response in the electron-doped cuprate superconductors is studied based on the t-t'-J model. It is shown that although the domelike shape of the doping dependent peak energy in the B 2g symmetry is a common feature for both electron-doped and hole-doped cuprate superconductors, there are pronounced deviations from a cubic response in the B 2g channel and a linear response in the B 2g channel for the electron-doped case in the low energy limit. It is also shown that these pronounced deviations are mainly caused by a nonmonotonic d-wave gap in the electron-doped cuprate superconductors.

Striking the Right Balance : Effectiveness of Anti-Doping Policies

NARCIS (Netherlands)

de Hon, O.M.

2016-01-01

Doping, and anti-doping, is in the news on a continuous basis. At the core of these stories and discussions is the question how effective anti-doping policies are to curb the use of doping in sports. Anti-doping policies are based on ethical values, a juridical framework, laboratory analyses,

Co-doping effects on luminescence and scintillation properties of Ce doped Lu3Al5O12 scintillator

International Nuclear Information System (INIS)

Kamada, Kei; Nikl, Martin; Kurosawa, Shunsuke; Beitlerova, Alena; Nagura, Aya; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

2015-01-01

The Mg, Ca, Sr and Ba 200 ppm co-doped Ce:Lu 3 Al 5 O 12 single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of the co-doping. The scintillation decays were accelerated by both Mg and Ca co-dopants. The Mg co-doped samples showed the fastest decay and the highest light yield among the co-doped samples

Carbon doped ZnO: Synthesis, characterization and interpretation

International Nuclear Information System (INIS)

Mishra, D.K.; Mohapatra, J.; Sharma, M.K.; Chattarjee, R.; Singh, S.K.; Varma, Shikha; Behera, S.N.; Nayak, Sanjeev K.; Entel, P.

2013-01-01

A novel thermal plasma in-flight technique has been adopted to synthesize nanocrystalline ZnO and carbon doped nanocrystalline ZnO matrix. Transmission electron microscopy (TEM) studies on these samples show the average particle sizes to be around 32 nm for ZnO and for carbon doped ZnO. An enhancement of saturation magnetization in nanosized carbon doped ZnO matrix by a factor of 3.8 has been found in comparison to ZnO nanoparticles at room temperature. Raman measurement clearly indicates the presence of Zn–C complexes surrounded by ZnO matrix in carbon doped ZnO. This indicates that the ferromagnetic signature in carbon doped ZnO arises from the creation of defects or the development of oxy-carbon clusters, in the carbon doped ZnO system. Theoretical studies based on density functional theory also support the experimental analyses. - Highlights: ► Synthesis of nanocrystalline ZnO and carbon doped ZnO matrix by inflight thermal plasma reactor. ► Enhancement of ferromagnetism in nanosized carbon doped ZnO in comparison to ZnO nanoparticles. ► Raman measurement indicates the presence of Zn–C complexes surrounded by ZnO matrix. ► Ferromagnetic signature in carbon doped ZnO arises from the development of oxy-carbon clusters. ► DFT supports experimental evidence of ferromagnetism in C doped ZnO nanoparticles.

Doping effect in Si nanocrystals

Science.gov (United States)

Li, Dongke; Xu, Jun; Zhang, Pei; Jiang, Yicheng; Chen, Kunji

2018-06-01

Intentional doping in semiconductors is a fundamental issue since it can control the conduction type and ability as well as modify the optical and electronic properties. To realize effective doping is the basis for developing semiconductor devices. However, by reducing the size of a semiconductor, like Si, to the nanometer scale, the doping effects become complicated due to the coupling between the quantum confinement effect and the surfaces and/or interfaces effect. In particular, by introducing phosphorus or boron impurities as dopants into material containing Si nanocrystals with a dot size of less than 10 nm, it exhibits different behaviors and influences on the physical properties from its bulk counterpart. Understanding the doping effects in Si nanocrystals is currently a challenge in order to further improve the performance of the next generation of nano-electronic and photonic devices. In this review, we present an overview of the latest theoretical studies and experimental results on dopant distributions and their effects on the electronic and optical properties of Si nanocrystals. In particular, the advanced characterization techniques on dopant distribution, the carrier transport process as well as the linear and nonlinear optical properties of doped Si nanocrystals, are systematically summarized.

Intended or Unintended Doping? A Review of the Presence of Doping Substances in Dietary Supplements Used in Sports

Directory of Open Access Journals (Sweden)

José Miguel Martínez-Sanz

2017-10-01

Full Text Available Introduction: The use of dietary supplements is increasing among athletes, year after year. Related to the high rates of use, unintentional doping occurs. Unintentional doping refers to positive anti-doping tests due to the use of any supplement containing unlisted substances banned by anti-doping regulations and organizations, such as the World Anti-Doping Agency (WADA. The objective of this review is to summarize the presence of unlabeled doping substances in dietary supplements that are used in sports. Methodology: A review of substances/metabolites/markers banned by WADA in ergonutritional supplements was completed using PubMed. The inclusion criteria were studies published up until September 2017, which analyzed the content of substances, metabolites and markers banned by WADA. Results: 446 studies were identified, 23 of which fulfilled all the inclusion criteria. In most of the studies, the purpose was to identify doping substances in dietary supplements. Discussion: Substances prohibited by WADA were found in most of the supplements analyzed in this review. Some of them were prohormones and/or stimulants. With rates of contamination between 12 and 58%, non-intentional doping is a point to take into account before establishing a supplementation program. Athletes and coaches must be aware of the problems related to the use of any contaminated supplement and should pay special attention before choosing a supplement, informing themselves fully and confirming the guarantees offered by the supplement.

Intended or Unintended Doping? A Review of the Presence of Doping Substances in Dietary Supplements Used in Sports

Science.gov (United States)

Mañas Ortiz, Christian; Ortiz-Moncada, Rocio

2017-01-01

Introduction: The use of dietary supplements is increasing among athletes, year after year. Related to the high rates of use, unintentional doping occurs. Unintentional doping refers to positive anti-doping tests due to the use of any supplement containing unlisted substances banned by anti-doping regulations and organizations, such as the World Anti-Doping Agency (WADA). The objective of this review is to summarize the presence of unlabeled doping substances in dietary supplements that are used in sports. Methodology: A review of substances/metabolites/markers banned by WADA in ergonutritional supplements was completed using PubMed. The inclusion criteria were studies published up until September 2017, which analyzed the content of substances, metabolites and markers banned by WADA. Results: 446 studies were identified, 23 of which fulfilled all the inclusion criteria. In most of the studies, the purpose was to identify doping substances in dietary supplements. Discussion: Substances prohibited by WADA were found in most of the supplements analyzed in this review. Some of them were prohormones and/or stimulants. With rates of contamination between 12 and 58%, non-intentional doping is a point to take into account before establishing a supplementation program. Athletes and coaches must be aware of the problems related to the use of any contaminated supplement and should pay special attention before choosing a supplement, informing themselves fully and confirming the guarantees offered by the supplement. PMID:28976928

Materials properties of hafnium and zirconium silicates: Metal interdiffusion and dopant penetration studies

Science.gov (United States)

Quevedo Lopez, Manuel Angel

Hafnium and Zirconium based gate dielectrics are considered potential candidates to replace SiO2 or SiON as the gate dielectric in CMOS processing. Furthermore, the addition of nitrogen into this pseudo-binary alloy has been shown to improve their thermal stability, electrical properties, and reduce dopant penetration. Because CMOS processing requires high temperature anneals (up to 1050°C), it is important to understand the diffusion properties of any metal associated with the gate dielectric in silicon at these temperatures. In addition, dopant penetration from the doped polysilicon gate into the Si channel at these temperatures must also be studied. Impurity outdiffusion (Hf, Zr) from the dielectric, or dopant (B, As, P) penetration through the dielectric into the channel region would likely result in deleterious effects upon the carrier mobility. In this dissertation extensive thermal stability studies of alternate gate dielectric candidates ZrSixOy and HfSixO y are presented. Dopant penetration studies from doped-polysilicon through HfSixOy and HfSixOyNz are also presented. Rutherford Backscattering Spectroscopy (RBS), Heavy Ion RBS (HI-RBS), X-ray Photoelectron Spectroscopy (XPS), High Resolution Transmission Electron Microscopy (HR-TEM), and Time of Flight and Dynamic Secondary Ion Mass Spectroscopy (ToF-SIMS, D-SIMS) methods were used to characterize these materials. The dopant diffusivity is calculated by modeling of the dopant profiles in the Si substrate. In this disseration is reported that Hf silicate films are more stable than Zr silicate films, from the metal interdiffusion point of view. On the other hand, dopant (B, As, and P) penetration is observed for HfSixO y films. However, the addition of nitrogen to the Hf - Si - O systems improves the dopant penetration properties of the resulting HfSi xOyNz films.

Silicon based multilayer photoelectrodes for photoelectrolysis of water to produce hydrogen from the sun

Science.gov (United States)

Faruque, Faisal

The main objective of this work is to study different materials for the direct photosynthesis of hydrogen from water. A variety of photocatalysts such as titanium dioxide, titanium oxy-nitride, silicon carbide, and gallium nitride are being investigated by others for the clean production of hydrogen for fuel cells and hydrogen economy. Our approach was to deposit suitable metallic regions on photocatalyst nanoparticles to direct the efficient synthesis of hydrogen to a particular site for convenient collection. We studied different electrode metals such as gold, platinum, titanium, palladium, and tungsten. We also studied different solar cell materials such as silicon (p- and n-types), silicon carbide and titanium dioxide semiconductors in order to efficiently generate electrons under illumination. We introduced a novel silicon-based multilayer photosynthesis device to take advantage of suitable properties of silicon and tungsten to efficiently produce hydrogen. The device consisted of a silicon (0.5mm) substrate, a deposited atomic layer of Al2O 3 (1nm), a doped polysilicon (0.1microm), and finally a tungsten nanoporous (5-10nm) layer acting as an interface electrode with water. The Al2O 3 layer was introduced to reduce leakage current and to prevent the spreading of the diffused p-n junction layer between the silicon and doped polysilicon layers. The surface of the photoelectrode was coated with nanotextured tungsten nanopores (TNP), which increased the surface area of the electrodes to the electrolyte, assisting in electron-hole mobility, and acting as a photocatalyst. The reported device exhibited a fill factor (%FF) of 27.22% and solar-to-hydrogen conversion efficiency of 0.03174%. This thesis describes the structures of the device, and offers a characterization and comparison between different photoelectrodes.

An accurate measurement of the baryonic Tully-Fisher relation with heavily gas-dominated ALFALFA galaxies

NARCIS (Netherlands)

Papastergis, E.; Adams, E. A. K.; van der Hulst, J. M.

2016-01-01

We use a sample of 97 galaxies selected from the Arecibo legacy fast ALFA (ALFALFA) 21 cm survey to make an accurate measurement of the baryonic Tully-Fisher relation (BTFR). These galaxies are specifically selected to be heavily gas-dominated (Mgas/M∗ ≳ 2.7) and to be oriented edge-on. The former

Plasmonic Properties of Silicon Nanocrystals Doped with Boron and Phosphorus.

Science.gov (United States)

Kramer, Nicolaas J; Schramke, Katelyn S; Kortshagen, Uwe R

2015-08-12

Degenerately doped silicon nanocrystals are appealing plasmonic materials due to silicon's low cost and low toxicity. While surface plasmonic resonances of boron-doped and phosphorus-doped silicon nanocrystals were recently observed, there currently is poor understanding of the effect of surface conditions on their plasmonic behavior. Here, we demonstrate that phosphorus-doped silicon nanocrystals exhibit a plasmon resonance immediately after their synthesis but may lose their plasmonic response with oxidation. In contrast, boron-doped nanocrystals initially do not exhibit plasmonic response but become plasmonically active through postsynthesis oxidation or annealing. We interpret these results in terms of substitutional doping being the dominant doping mechanism for phosphorus-doped silicon nanocrystals, with oxidation-induced defects trapping free electrons. The behavior of boron-doped silicon nanocrystals is more consistent with a strong contribution of surface doping. Importantly, boron-doped silicon nanocrystals exhibit air-stable plasmonic behavior over periods of more than a year.

Comparative study of Tm-doped and Tm-Sc co-doped Lu3Al5O12 scintillator

International Nuclear Information System (INIS)

Sugiyama, Makoto; Yanagida, Takayuki; Fujimoto, Yutaka

2014-01-01

The crystals of Tm doped and Tm-Sc co-doped Lu 3 Al 5 O 12 (LuAG) grown by the floating zone (FZ) method were examined for their optical and scintillation properties. In transmittance spectra, strong absorption lines due to Tm 3+ 4f–4f transitions were observed. X-ray excited radioluminescence spectra were measured and broad and sharp emission peaks were detected. The former one was attributed to Sc 3+ and the latter one was due to Tm 3+ 4f–4f transitions. Scintillation yield enhancement due to Sc co-doping was observed by means of 137 Cs pulse height spectra. Scintillation decay times were several tens of μs under pulse X-ray excitation. - Highlights: • LuAG:Tm and LuAG:Tm, Sc single crystals have been grown by the FZ method. • Tm 3+ 4f–4f absorption has been observed in transmittance spectra. • Scintillation yield of Tm-doped LuAG has been enhanced by Sc co-doping

The Development of the World Anti-Doping Code.

Science.gov (United States)

Young, Richard

2017-01-01

This chapter addresses both the development and substance of the World Anti-Doping Code, which came into effect in 2003, as well as the subsequent Code amendments, which came into effect in 2009 and 2015. Through an extensive process of stakeholder input and collaboration, the World Anti-Doping Code has transformed the hodgepodge of inconsistent and competing pre-2003 anti-doping rules into a harmonized and effective approach to anti-doping. The Code, as amended, is now widely recognized worldwide as the gold standard in anti-doping. The World Anti-Doping Code originally went into effect on January 1, 2004. The first amendments to the Code went into effect on January 1, 2009, and the second amendments on January 1, 2015. The Code and the related international standards are the product of a long and collaborative process designed to make the fight against doping more effective through the adoption and implementation of worldwide harmonized rules and best practices. © 2017 S. Karger AG, Basel.

Photoluminescence and doping mechanism of theranostic Eu3+/Fe3+ dual-doped hydroxyapatite nanoparticles

Science.gov (United States)

Chen, Min-Hua; Yoshioka, Tomohiko; Ikoma, Toshiyuki; Hanagata, Nobutaka; Lin, Feng-Huei; Tanaka, Junzo

2014-10-01

Theranostic nanoparticles currently have been regarded as an emerging concept of ‘personalized medicine’ with diagnostic and therapeutic dual-functions. Eu3+ doped hydroxyapatite (HAp) has been regarded as a promising fluorescent probe for in vivo imaging applications. Additionally, substitution of Ca2+ with Fe3+ in HAp crystal may endow the capability of producing heat upon exposure to a magnetic field. Here we report a preliminary study of doping mechanism and photoluminescence of Eu3+ and Fe3+ doped HAp nanoparticles (Eu/Fe:HAp). HAp with varied concentration of Eu3+ and Fe3+ doping are presented as Eu(10 mol%):HAp, Eu(7 mol%)-Fe(3 mol%):HAp, Eu(5 mol%)-Fe(5 mol%):HAp, Eu(3 mol%)-Fe(7 mol%):HAp, and Fe(10 mol%):HAp in the study. The results showed that the HAp particles, in nano-size with rod-like morphology, were successfully doped with Eu3+ and Fe3+, and the particles can be well suspended in cell culture medium. Photoluminescence analysis revealed that particles have prominent emissions at 536 nm, 590 nm, 615 nm, 650 nm and 695 nm upon excitation at a wavelength of 397 nm. Moreover, these Eu/Fe:HAp nanoparticles belonged to B-type carbonated HAp, which has been considered an effective biodegradable and biocompatible drug/gene carrier in biological applications.

Photoluminescence and doping mechanism of theranostic Eu3+/Fe3+ dual-doped hydroxyapatite nanoparticles

International Nuclear Information System (INIS)

Chen, Min-Hua; Lin, Feng-Huei; Yoshioka, Tomohiko; Ikoma, Toshiyuki; Tanaka, Junzo; Hanagata, Nobutaka

2014-01-01

Theranostic nanoparticles currently have been regarded as an emerging concept of ‘personalized medicine’ with diagnostic and therapeutic dual-functions. Eu 3+ doped hydroxyapatite (HAp) has been regarded as a promising fluorescent probe for in vivo imaging applications. Additionally, substitution of Ca 2+ with Fe 3+ in HAp crystal may endow the capability of producing heat upon exposure to a magnetic field. Here we report a preliminary study of doping mechanism and photoluminescence of Eu 3+ and Fe 3+ doped HAp nanoparticles (Eu/Fe:HAp). HAp with varied concentration of Eu 3+ and Fe 3+ doping are presented as Eu(10 mol%):HAp, Eu(7 mol%)-Fe(3 mol%):HAp, Eu(5 mol%)-Fe(5 mol%):HAp, Eu(3 mol%)-Fe(7 mol%):HAp, and Fe(10 mol%):HAp in the study. The results showed that the HAp particles, in nano-size with rod-like morphology, were successfully doped with Eu 3+ and Fe 3+ , and the particles can be well suspended in cell culture medium. Photoluminescence analysis revealed that particles have prominent emissions at 536 nm, 590 nm, 615 nm, 650 nm and 695 nm upon excitation at a wavelength of 397 nm. Moreover, these Eu/Fe:HAp nanoparticles belonged to B-type carbonated HAp, which has been considered an effective biodegradable and biocompatible drug/gene carrier in biological applications. (paper)

Photoluminescence and doping mechanism of theranostic Eu3+/Fe3+ dual-doped hydroxyapatite nanoparticles.

Science.gov (United States)

Chen, Min-Hua; Yoshioka, Tomohiko; Ikoma, Toshiyuki; Hanagata, Nobutaka; Lin, Feng-Huei; Tanaka, Junzo

2014-10-01

Theranostic nanoparticles currently have been regarded as an emerging concept of 'personalized medicine' with diagnostic and therapeutic dual-functions. Eu 3+ doped hydroxyapatite (HAp) has been regarded as a promising fluorescent probe for in vivo imaging applications. Additionally, substitution of Ca 2+ with Fe 3+ in HAp crystal may endow the capability of producing heat upon exposure to a magnetic field. Here we report a preliminary study of doping mechanism and photoluminescence of Eu 3+ and Fe 3+ doped HAp nanoparticles (Eu/Fe:HAp). HAp with varied concentration of Eu 3+ and Fe 3+ doping are presented as Eu(10 mol%):HAp, Eu(7 mol%)-Fe(3 mol%):HAp, Eu(5 mol%)-Fe(5 mol%):HAp, Eu(3 mol%)-Fe(7 mol%):HAp, and Fe(10 mol%):HAp in the study. The results showed that the HAp particles, in nano-size with rod-like morphology, were successfully doped with Eu 3+ and Fe 3+ , and the particles can be well suspended in cell culture medium. Photoluminescence analysis revealed that particles have prominent emissions at 536 nm, 590 nm, 615 nm, 650 nm and 695 nm upon excitation at a wavelength of 397 nm. Moreover, these Eu/Fe:HAp nanoparticles belonged to B-type carbonated HAp, which has been considered an effective biodegradable and biocompatible drug/gene carrier in biological applications.

Electrical properties of tin-doped zinc oxide nanostructures doped at different dopant concentrations

International Nuclear Information System (INIS)

Nasir, M. F.; Zainol, M. N.; Hannas, M.; Mamat, M. H.; Rusop, Mohamad; Rahman, S. A.

2016-01-01

This project has been focused on the electrical and optical properties respectively on the effect of Tin doped zinc oxide (ZnO) thin films at different dopant concentrations. These thin films were doped with different Sn dopant concentrations at 1 at%, 2 at%, 3 at%, 4 at% and 5 at% was selected as the parameter to optimize the thin films quality while the annealing temperature is fixed 500 °C. Sn doped ZnO solutions were deposited onto the glass substrates using sol-gel spin coating method. This project was involved with three phases, which are thin films preparation, deposition and characterization. The thin films were characterized using Current Voltage (I-V) measurement and ultraviolet-visible-near-infrared (UV-vis-NIR) spectrophotometer (Perkin Elmer Lambda 750) for electrical properties and optical properties. The electrical properties show that the resistivity is the lowest at 4 at% Sn doping concentration with the value 3.08 × 10"3 Ωcm"−"1. The absorption coefficient spectrum obtained shows all films exhibit very low absorption in the visible (400-800 nm) and near infrared (NIR) (>800 nm) range but exhibit high absorption in the UV range.

Electrical properties of tin-doped zinc oxide nanostructures doped at different dopant concentrations

Energy Technology Data Exchange (ETDEWEB)

Nasir, M. F., E-mail: babaibaik2002@yahoo.com; Zainol, M. N., E-mail: nizarzainol@yahoo.com; Hannas, M., E-mail: mhannas@gmail.com [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Mamat, M. H., E-mail: mhmamat@salam.uitm.edu.my; Rusop, Mohamad, E-mail: rusop@salam.uitm.edu.my [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); NANO-SciTech Centre (NST), Institute of Science (IOS), Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia); Rahman, S. A., E-mail: saadah@um.edu.my [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Low Dimensional Materials Research Centre, Physics Department, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2016-07-06

This project has been focused on the electrical and optical properties respectively on the effect of Tin doped zinc oxide (ZnO) thin films at different dopant concentrations. These thin films were doped with different Sn dopant concentrations at 1 at%, 2 at%, 3 at%, 4 at% and 5 at% was selected as the parameter to optimize the thin films quality while the annealing temperature is fixed 500 °C. Sn doped ZnO solutions were deposited onto the glass substrates using sol-gel spin coating method. This project was involved with three phases, which are thin films preparation, deposition and characterization. The thin films were characterized using Current Voltage (I-V) measurement and ultraviolet-visible-near-infrared (UV-vis-NIR) spectrophotometer (Perkin Elmer Lambda 750) for electrical properties and optical properties. The electrical properties show that the resistivity is the lowest at 4 at% Sn doping concentration with the value 3.08 × 10{sup 3} Ωcm{sup −1}. The absorption coefficient spectrum obtained shows all films exhibit very low absorption in the visible (400-800 nm) and near infrared (NIR) (>800 nm) range but exhibit high absorption in the UV range.

Disorder-induced enhancement of conductance in doped nanowires

Institute of Scientific and Technical Information of China (English)

Xu Ning; Wang Bao-Lin; Sun Hou-Qian; Kong Fan-Jie

2010-01-01

A new mechanism is proposed to explain the enhancement of conductance in doped nanowires. It is shown that the anomalous enhancement of conductance is due to surface doping. The conductance in doped nanowires increases with dopant concentration, which is qualitatively consistent with the existing experimental results. In addition, the I-V curves are linear and thus suggest that the metal electrodes make ohmic contacts to the shell-doped nanowires.The electric current increases with wire diameter (D) and decreases exponentially with wire length (L). Therefore, the doped nanowires have potential application in nanoscale electronic and optoelectronic devices.

Synthesis and characterization of chromium doped boehmite nanofibres

International Nuclear Information System (INIS)

Yang Jing; Frost, Ray L.; Yuan Yong

2009-01-01

Thermogravimetric and differential thermogravimetric analysis has been used to study synthesised chromium doped boehmite. The dehydroxylation temperature increases significantly from 0 to 5% doping, after which the dehydroxylation temperature shows a small steady increase up to the 20% doping level. The temperature of dehydroxylation increases with time of hydrothermal treatment. Chromium doped boehmite nanofibres were also characterised by X-ray diffraction and transmission electron microscopy. Hydrothermal treatment of doped boehmite with chromium resulted in the formation of nanofibres over a wide dopant range. Nanofibres up to 500 nm in length and between 4 and 6 nm in width were produced

Hormones as doping in sports.

Science.gov (United States)

Duntas, Leonidas H; Popovic, Vera

2013-04-01

Though we may still sing today, as did Pindar in his eighth Olympian Victory Ode, "… of no contest greater than Olympia, Mother of Games, gold-wreathed Olympia…", we must sadly admit that today, besides blatant over-commercialization, there is no more ominous threat to the Olympic games than doping. Drug-use methods are steadily becoming more sophisticated and ever harder to detect, increasingly demanding the use of complex analytical procedures of biotechnology and molecular medicine. Special emphasis is thus given to anabolic androgenic steroids, recombinant growth hormone and erythropoietin as well as to gene doping, the newly developed mode of hormones abuse which, for its detection, necessitates high-tech methodology but also multidisciplinary individual measures incorporating educational and psychological methods. In this Olympic year, the present review offers an update on the current technologically advanced endocrine methods of doping while outlining the latest procedures applied-including both the successes and pitfalls of proteomics and metabolomics-to detect doping while contributing to combating this scourge.

Room temperature ferromagnetism in Mn-doped NiO nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Layek, Samar, E-mail: samarlayek@gmail.com; Verma, H.C.

2016-01-01

Mn-doped NiO nanoparticles of the series Ni{sub 1−x}Mn{sub x}O (x=0.00, 0.02, 0.04 and 0.06) are successfully synthesized using a low temperature hydrothermal method. Samples up to 6% Mn-doping are single phase in nature as observed from powder x-ray diffraction (XRD) studies. Rietveld refinement of the XRD data shows that all the single phase samples crystallize in the NaCl like fcc structure with space group Fm-3m. Unit cell volume decreases with increasing Mn-doping. Pure NiO nanoparticles show weak ferromagnetism, may be due to nanosize nature. Introduction of Mn within NiO lattice improves the magnetic properties significantly. Room temperature ferromagnetism is found in all the doped samples whereas the magnetization is highest for 2% Mn-doping and then decreases with further doping. The ZFC and FC branches in the temperature dependent magnetization separate well above 350 K indicating transition temperature well above room temperature for 2% Mn-doped NiO Nanoparticle. The ferromagnetic Curie temperature is found to be 653 K for the same sample as measured by temperature dependent magnetization study using vibrating sample magnetometer (VSM) in high vacuum. - Highlights: • Mn-doped NiO nanoparticles are prepared by a simple hydrothermal method. • Unit cell volume decreases with increasing doping concentration. • Mn-doping leads to room temperature ferromagnetism in NiO nanoparticles. • Magnetization is highest for 2% Mn-doping. • Above 2%, magnetization decreases with increasing doping.

Room temperature ferromagnetism in Mn-doped NiO nanoparticles

International Nuclear Information System (INIS)

Layek, Samar; Verma, H.C.

2016-01-01

Mn-doped NiO nanoparticles of the series Ni_1_−_xMn_xO (x=0.00, 0.02, 0.04 and 0.06) are successfully synthesized using a low temperature hydrothermal method. Samples up to 6% Mn-doping are single phase in nature as observed from powder x-ray diffraction (XRD) studies. Rietveld refinement of the XRD data shows that all the single phase samples crystallize in the NaCl like fcc structure with space group Fm-3m. Unit cell volume decreases with increasing Mn-doping. Pure NiO nanoparticles show weak ferromagnetism, may be due to nanosize nature. Introduction of Mn within NiO lattice improves the magnetic properties significantly. Room temperature ferromagnetism is found in all the doped samples whereas the magnetization is highest for 2% Mn-doping and then decreases with further doping. The ZFC and FC branches in the temperature dependent magnetization separate well above 350 K indicating transition temperature well above room temperature for 2% Mn-doped NiO Nanoparticle. The ferromagnetic Curie temperature is found to be 653 K for the same sample as measured by temperature dependent magnetization study using vibrating sample magnetometer (VSM) in high vacuum. - Highlights: • Mn-doped NiO nanoparticles are prepared by a simple hydrothermal method. • Unit cell volume decreases with increasing doping concentration. • Mn-doping leads to room temperature ferromagnetism in NiO nanoparticles. • Magnetization is highest for 2% Mn-doping. • Above 2%, magnetization decreases with increasing doping.

AFM of metallic nano-particles and nano-structures in heavily irradiated NaCl

OpenAIRE

Gaynutdinov, R; Vainshtein, DI; Hak, SJ; Tolstikhina, A; Den Hartog, HW

2003-01-01

AFM investigations are reported for heavily, electron irradiated NaCl crystals in ultra high vacuum (UHV) in the non-contact mode-with an UHV AFM/STM Omicron system. To avoid chemical reactions between the radiolytic Na and oxygen and water, the irradiated samples were cleaved and prepared for the experiments in UHV At the surface of freshly cleaved samples, we have observed sodium nano-precipitates with shapes, which depend on the irradiation dose and the volume fraction of the radiolytic Na...

Stored energy and annealing behavior of heavily deformed aluminium

DEFF Research Database (Denmark)

Kamikawa, Naoya; Huang, Xiaoxu; Kondo, Yuka

2012-01-01

It has been demonstrated in previous work that a two-step annealing treatment, including a low-temperature, long-time annealing and a subsequent high-temperature annealing, is a promising route to control the microstructure of a heavily deformed metal. In the present study, structural parameters...... are quantified such as boundary spacing, misorientation angle and dislocation density for 99.99% aluminium deformed by accumulative roll-bonding to a strain of 4.8. Two different annealing processes have been applied; (i) one-step annealing for 0.5 h at 100-400°C and (ii) two-step annealing for 6 h at 175°C...... followed by 0.5 h annealing at 200-600°C, where the former treatment leads to discontinuous recrystallization and the latter to uniform structural coarsening. This behavior has been analyzed in terms of the relative change during annealing of energy stored as elastic energy in the dislocation structure...

Potassium doped MWCNTs for hydrogen storage enhancement

International Nuclear Information System (INIS)

Adabi Qomi, S.; Gashtasebi, M.; Khoshnevisan, B.

2012-01-01

Here we have used potassium doped MWCNTs for enhancement of hydrogen storage process. XRD and SEM images have confirmed the doping of potassium. For studying the storage process a hydrogenic battery set up has been used. In the battery the working electrode has been made of the silver foam deposited by the doped MWCNTs electrophoretically.

Mapping the electromagnetic field confinement in the gap of germanium nanoantennas with plasma wavelength of 4.5 micrometers

NARCIS (Netherlands)

Calandrini, Eugenio; Venanzi, Tommaso; Appugliese, Felice; Badioli, Michela; Giliberti, Valeria; Baldassarre, Leonetta; Biagioni, Paolo; De Angelis, Francesco; Klesse, Wolfgang M.; Scappucci, G.; Ortolani, Michele

2016-01-01

We study plasmonic nanoantennas for molecular sensing in the mid-infrared made of heavily doped germanium, epitaxially grown with a bottom-up doping process and featuring free carrier density in excess of 10²⁰ cm^-3. The dielectric function of the 250 nm thick germanium film

Iron solubility in highly boron-doped silicon

International Nuclear Information System (INIS)

McHugo, S.A.; McDonald, R.J.; Smith, A.R.; Hurley, D.L.; Weber, E.R.

1998-01-01

We have directly measured the solubility of iron in high and low boron-doped silicon using instrumental neutron activation analysis. Iron solubilities were measured at 800, 900, 1000, and 1100thinsp degree C in silicon doped with either 1.5x10 19 or 6.5x10 14 thinspboronthinspatoms/cm 3 . We have measured a greater iron solubility in high boron-doped silicon as compared to low boron-doped silicon, however, the degree of enhancement is lower than anticipated at temperatures >800thinsp degree C. The decreased enhancement is explained by a shift in the iron donor energy level towards the valence band at elevated temperatures. Based on this data, we have calculated the position of the iron donor level in the silicon band gap at elevated temperatures. We incorporate the iron energy level shift in calculations of iron solubility in silicon over a wide range of temperatures and boron-doping levels, providing a means to accurately predict iron segregation between high and low boron-doped silicon. copyright 1998 American Institute of Physics

Progress on erbium-doped waveguide components

DEFF Research Database (Denmark)

Bjarklev, Anders Overgaard; Berendt, Martin Ole; Broeng, Jes

1997-01-01

The recent development in erbium-doped fiber amplifiers, and fiber lasers is reviewed. Also the latest results on planar erbium-doped waveguide amplifiers and high erbium concentration characterisation methods are presented...

Base profile design for high-performance operation of bipolar transistors at liquid-nitrogen temperature

International Nuclear Information System (INIS)

Stork, J.M.C.; Harame, D.L.; Meyerson, B.S.; Nguyen, T.N.

1989-01-01

The base profile requirements of Si bipolar junction transistors (BJT's) high-performance operation at liquid-nitrogen temperature are examined. Measurements of thin epitaxial-base polysilicon-emitter n-p-n transistors with increasing base doping show the effects of bandgap narrowing, mobility changes, and carrier freezeout. At room temperature the collector current at low injection is proportional to the integrated base charge, independent of the impurity distribution. At temperatures below 150 Κ, however, minority injection is dominated by the peak base doping because of the greater effectiveness of bandgap narrowing. When the peak doping in the base approaches 10 19 cm -3 , the bandgap difference between emitter and base is sufficiently small that the current gain no longer monotonically decreases with lower temperature but instead shows a maximum as low as 180 Κ. The device design window appears limited at the low-current end by increased base-emitter leakage due to tunneling and by resistance control at the high-current end. Using the measured dc characteristics, circuit delay calculations are made to estimate the performance of an ECL ring oscillator at room and liquid-nitrogen temperatures. It is shown that if the base doping can be raised to 10 19 cm -3 while keeping the base thickness constant, the minimum delay at liquid nitrogen can approach the delay of optimized devices at room temperature

Erbium doped stain etched porous silicon

International Nuclear Information System (INIS)

Gonzalez-Diaz, B.; Diaz-Herrera, B.; Guerrero-Lemus, R.; Mendez-Ramos, J.; Rodriguez, V.D.; Hernandez-Rodriguez, C.; Martinez-Duart, J.M.

2008-01-01

In this work a simple erbium doping process applied to stain etched porous silicon layers (PSLs) is proposed. This doping process has been developed for application in porous silicon solar cells, where conventional erbium doping processes are not affordable because of the high processing cost and technical difficulties. The PSLs were formed by immersion in a HF/HNO 3 solution to properly adjust the porosity and pore thickness to an optimal doping of the porous structure. After the formation of the porous structure, the PSLs were analyzed by means of nitrogen BET (Brunauer, Emmett and Teller) area measurements and scanning electron microscopy. Subsequently, the PSLs were immersed in a saturated erbium nitrate solution in order to cover the porous surface. Then, the samples were subjected to a thermal process to activate the Er 3+ ions. Different temperatures and annealing times were used in this process. The photoluminescence of the PSLs was evaluated before and after the doping processes and the composition was analyzed by Fourier transform IR spectroscopy

Cobalt doped proangiogenic hydroxyapatite for bone tissue engineering application

International Nuclear Information System (INIS)

Kulanthaivel, Senthilguru; Roy, Bibhas; Agarwal, Tarun; Giri, Supratim; Pramanik, Krishna; Pal, Kunal; Ray, Sirsendu S.; Maiti, Tapas K.; Banerjee, Indranil

2016-01-01

ABSTRACT: The present study delineates the synthesis and characterization of cobalt doped proangiogenic–osteogenic hydroxyapatite. Hydroxyapatite samples, doped with varying concentrations of bivalent cobalt (Co"2"+) were prepared by the ammoniacal precipitation method and the extent of doping was measured by ICP–OES. The crystalline structure of the doped hydroxyapatite samples was confirmed by XRD and FTIR studies. Analysis pertaining to the effect of doped hydroxyapatite on cell cycle progression and proliferation of MG-63 cells revealed that the doping of cobalt supported the cell viability and proliferation up to a threshold limit. Furthermore, such level of doping also induced differentiation of the bone cells, which was evident from the higher expression of differentiation markers (Runx2 and Osterix) and better nodule formation (SEM study). Western blot analysis in conjugation with ELISA study confirmed that the doped HAp samples significantly increased the expression of HIF-1α and VEGF in MG-63 cells. The analysis described here confirms the proangiogenic–osteogenic properties of the cobalt doped hydroxyapatite and indicates its potential application in bone tissue engineering. - Highlights: • Cobalt (Co"+"2) doped hydroxyapatite (Co-HAp) can be prepared by the wet chemical method. • The concentration of Co"+"2 influences the physico-chemical properties of HAp. • Co-HAp was found to be biocompatible and osteogenic. • Co-HAp enhanced cellular VEGF secretion through HIF-1α stabilization. • The optimum biological performance of Co-HAp was achieved for 0.33% (w/w) Co"+"2 doping.

Effects of CuO co-doping on γ-ray irradiation resistance of active ions doped phosphate glasses

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhihuan [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); ENEA-UTTMAT, Via Anguillarese 301, 00123 Rome (Italy); Baccaro, Stefania; Cemmi, Alessia [ENEA-UTTMAT, Via Anguillarese 301, 00123 Rome (Italy); Shen, Wei [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Chen, Guorong, E-mail: grchen@ecust.edu.cn [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)

2013-09-15

The effect of copper ion doping on the γ-ray irradiation resistance of Mn{sup 2+} and Pr{sup 3+} doped phosphate glasses has been studied. UV–visible transmission spectra and photoluminescence spectra have been measured before and after γ-irradiation to characterize the radiation-induced defects. The electron paramagnetic resonance spectra of the irradiated samples with, and without Cu ions have been compared to show the ability of Cu ions to suppress the generation of radiation-induced color centers. The differential transmission spectra and the radiation-induced absorption coefficients have also been calculated for discussion of the observed phenomena. The much improved γ-irradiation resistance of Mn{sup 2+} and Pr{sup 3+} doped phosphate glasses has been demonstrated through CuO co-doping.

The evolving science of detection of 'blood doping'.

Science.gov (United States)

Lundby, Carsten; Robach, Paul; Saltin, Bengt

2012-03-01

Blood doping practices in sports have been around for at least half a century and will likely remain for several years to come. The main reason for the various forms of blood doping to be common is that they are easy to perform, and the effects on exercise performance are gigantic. Yet another reason for blood doping to be a popular illicit practice is that detection is difficult. For autologous blood transfusions, for example, no direct test exists, and the direct testing of misuse with recombinant human erythropoietin (rhEpo) has proven very difficult despite a test exists. Future blood doping practice will likely include the stabilization of the transcription factor hypoxia-inducible factor which leads to an increased endogenous erythropoietin synthesis. It seems unrealistic to develop specific test against such drugs (and the copies hereof originating from illegal laboratories). In an attempt to detect and limit blood doping, the World Anti-Doping Agency (WADA) has launched the Athlete Biological Passport where indirect markers for all types of blood doping are evaluated on an individual level. The approach seemed promising, but a recent publication demonstrates the system to be incapable of detecting even a single subject as 'suspicious' while treated with rhEpo for 10-12 weeks. Sad to say, the hope that the 2012 London Olympics should be cleaner in regard to blood doping seems faint. We propose that WADA strengthens the quality and capacities of the National Anti-Doping Agencies and that they work more efficiently with the international sports federations in an attempt to limit blood doping. © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.

Calcium decorated and doped phosphorene for gas adsorption

Energy Technology Data Exchange (ETDEWEB)

Lalitha, Murugan; Nataraj, Yuvarani; Lakshmipathi, Senthilkumar, E-mail: lsenthilkumar@buc.edu.in

2016-07-30

Highlights: • Phosphorene exhibits n-type/p-type nature on decorating/doping calcium respectively. • Gas molecules (CH{sub 4}, CO{sub 2}, H{sub 2} and NH{sub 3}) are physisorbed on phosphorene. • Ca decorated Phosphorene is recommended for high density hydrogen storage applications. • Calcium doping on zigzag and armchair sites makes phosphorene more reactive. • CH{sub 4}, CO{sub 2}, H{sub 2} prefer Ca-doped on zigzag1 site, whereas ammonia prefers Ca-doped on armchair. - Abstract: In this paper, we present the results from first-principles study based on the electronic structure and adsorption characteristics of CH{sub 4}, CO{sub 2}, H{sub 2} and NH{sub 3} adsorbed on Ca decorated/doped phosphorene. Our study finds that phosphorene exhibits n-type behaviour on decorating calcium, and p-type on doping calcium. Gas molecules are physisorbed on both pristine and calcium-mediated phosphorene, visible through their lower binding energy and charge transfer values. Ca decorated phosphorene is suitable for hydrogen storage due to its higher binding energy for H{sub 2}. Ca doped structures shows increased binding affinity towards CH{sub 4} and NH{sub 3} in zigzag1 direction and armchair directions respectively. The extracts of our study implies that Ca doped phosphorene possess increased binding affinity towards gas molecules, and the results are highly helpful for gas adsorption and to design gas sensors based on calcium doped or decorated phosphorene.

Effect of doping concentration on the structural, morphological, optical and electrical properties of Mn-doped CdO thin films

Directory of Open Access Journals (Sweden)

Manjula N.

2015-12-01

Full Text Available Thin films of manganese-doped cadmium oxide (CdO:Mn with different Mn-doping levels (0, 1, 2, 3 and 4 at.% were deposited on glass substrates by employing an inexpensive, simplified spray technique using a perfume atomizer at 375 °C. The influence of Mn incorporation on the structural, morphological, optical and electrical properties of CdO films has been studied. All the films exhibit cubic crystal structure with a (1 1 1 preferential orientation. Mn-doping causes a slight shift of the (1 1 1 diffraction peak towards higher angle. The crystallite size of the films is found to decrease from 34.63 nm to 17.68 nm with an increase in Mn doping concentration. The CdO:Mn film coated with 1 at.% Mn exhibit a high transparency of nearly 90 % which decreases for higher doping concentration. The optical band gap decreases with an increase in Mn doping concentration. All the films have electrical resistivity of the order of 10−4 Ω·cm.

Doping enhanced barrier lowering in graphene-silicon junctions

Science.gov (United States)

Zhang, Xintong; Zhang, Lining; Chan, Mansun

2016-06-01

Rectifying properties of graphene-semiconductor junctions depend on the Schottky barrier height. We report an enhanced barrier lowering in graphene-Si junction and its essential doping dependence in this paper. The electric field due to ionized charge in n-type Si induces the same type doping in graphene and contributes another Schottky barrier lowering factor on top of the image-force-induced lowering (IFIL). We confirm this graphene-doping-induced lowering (GDIL) based on well reproductions of the measured reverse current of our fabricated graphene-Si junctions by the thermionic emission theory. Excellent matching between the theoretical predictions and the junction data of the doping-concentration dependent barrier lowering serves as another evidence of the GDIL. While both GDIL and IFIL are enhanced with the Si doping, GDIL exceeds IFIL with a threshold doping depending on the as-prepared graphene itself.

Neutron transmutation doping

Energy Technology Data Exchange (ETDEWEB)

Jun, Byung Jin

2001-09-01

HE OVERALL STATE OF THE ART RELATED WITH NEUTRON TRANSMUTATION DOPING(NCT) IS SURVEYED. ITEMS RELATED FOR THE REALIZATION OF NTD IN HANARO IS FOCUSED. IN ADDITION TO THE UNIFORM IRRADIATION AND ACHIEVING THE TARGET RESISTIVITY WHICH ARE THE MOST IMPORTANT TECHNICAL REQUIREMENTS FOR THE NTD, OTHER ITEMS SUCH AS THE FUNCTION AND ROLE OF NTD, MARKET TREND, QUALITY CONTROL ARE INCLUDED. MEANWHILE THE ONLY ADVANTAGE OF NTD IS ACHIEVING VERY HIGH UNIFORMITY OF DOPING, IT HAS SEVERAL DISADVANTAGES DUE TO THE USE OF NUCLEAR REACTOR. THEREFORE THE SEMICONDUCTOR INDUSTRY HAS CONTINUED DEVELOPMENT OF TECHNOLOGY TO REPLACE NTD, AND THE DEMAND OF NTD HAD BEEN DECREASED A LOT DURING 1990S. AS THE DEMAND FOR LARGE CRYSTAL INCREASES, HOWEVER, THE NTD DEMAND BEGAN TO INCREASE AGAIN FROM 2000. SINCE THE DEMAND FOR THE LARGER CRYSTAL WILL BE CONTINUED IN THE FUTURE, THE ROLE OF NTD WOULD BE NEEDED FOR THE LONGER TIME. IN ORDER TO MITIGATE THIS TREND OF DEMAND, THE REACTOR SHOULD BE CAPABLE OF ACCEPTING LARGE CRYSTAL AND THE EFFORT TO IMPROVE DOPING UNIFORMITY AND TO REDUCE THE COST SHOULD CONTINUED.

Cobalt doped proangiogenic hydroxyapatite for bone tissue engineering application.

Science.gov (United States)

Kulanthaivel, Senthilguru; Roy, Bibhas; Agarwal, Tarun; Giri, Supratim; Pramanik, Krishna; Pal, Kunal; Ray, Sirsendu S; Maiti, Tapas K; Banerjee, Indranil

2016-01-01

The present study delineates the synthesis and characterization of cobalt doped proangiogenic-osteogenic hydroxyapatite. Hydroxyapatite samples, doped with varying concentrations of bivalent cobalt (Co(2+)) were prepared by the ammoniacal precipitation method and the extent of doping was measured by ICP-OES. The crystalline structure of the doped hydroxyapatite samples was confirmed by XRD and FTIR studies. Analysis pertaining to the effect of doped hydroxyapatite on cell cycle progression and proliferation of MG-63 cells revealed that the doping of cobalt supported the cell viability and proliferation up to a threshold limit. Furthermore, such level of doping also induced differentiation of the bone cells, which was evident from the higher expression of differentiation markers (Runx2 and Osterix) and better nodule formation (SEM study). Western blot analysis in conjugation with ELISA study confirmed that the doped HAp samples significantly increased the expression of HIF-1α and VEGF in MG-63 cells. The analysis described here confirms the proangiogenic-osteogenic properties of the cobalt doped hydroxyapatite and indicates its potential application in bone tissue engineering. Copyright © 2015 Elsevier B.V. All rights reserved.

Characteristic analysis on the physical properties of nanostructured Mg-doped CdO thin films—Doping concentration effect

Directory of Open Access Journals (Sweden)

K. Usharani

2015-06-01

Full Text Available Highly conductive and transparent magnesium-doped cadmium oxide (CdO:Mg thin films have been deposited on suitably cleaned glass substrates maintained at 375 °C by spray pyrolysis technique using perfume atomizer. The magnesium content in the films is varied from 0 to 8 at% in steps of 2 at%. The effect of Mg doping on the structural, morphological, optical and electrical properties of the CdO thin films has been studied. All the films exhibited cubic structure with a preferential orientation along the (1 1 1 plane irrespective of the Mg doping level. SEM analysis showed that the film morphology modifies from spherical shaped grains to closely packed cauliflower shaped nanostructures with Mg doping. Except for the film coated with 2 at% Mg dopant, all the other doped films exhibited a blue shift in the optical band gap. Electrical studies revealed that the CdO:Mg film coated with 8 at% Mg dopant had a minimum resistivity of 0.0853×101 Ω-cm.

Continuous Czochralski growth: Silicon sheet growth development of the large area sheet task of the low cost silicon solar array project

Science.gov (United States)

Johnson, C. M.

1980-12-01

The growth of 100 kg of silicon single crystal material, ten cm in diameter or greater, and 150 kg of silicon single crystal material 15 cm or greater utilizing one common silicon container material (one crucible) is investigated. A crystal grower that is recharged with a new supply of polysilicon material while still under vacuum and at temperatures above the melting point of silicon is developed. It accepts large polysilicon charges up to 30 kg, grows large crystal ingots (to 15 cm diameter and 25 kg in weight), and holds polysilicon material for recharging (rod or lump) while, at the same time, growing crystal ingots. Special equipment is designed to recharge polysilicon rods, recharge polysilicon lumps, and handle and store large, hot silicon crystal ingots. Many continuous crystal growth runs were performed lasting as long as 109 hours and producing as many as ten crystal ingots, 15 cm with weights progressing to 27 kg.

Fabrication and characterization of Pd/Cu doped ZnO/Si and Ni/Cu doped ZnO/Si Schottky diodes

Energy Technology Data Exchange (ETDEWEB)

Agarwal, Lucky; Singh, Brijesh Kumar; Tripathi, Shweta [Department of Electronics & Communication Engineering, Motilal Nehru National Institute of Technology, Allahabad 211004 (India); Chakrabarti, P., E-mail: pchakrabarti.ece@iitbhu.ac.in [Department of Electronics & Communication Engineering, Motilal Nehru National Institute of Technology, Allahabad 211004 (India); Department of Electronics Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

2016-08-01

In this paper, fabrication and characterization of copper doped ZnO (Cu doped ZnO) based Schottky devices have been reported. Cu doped ZnO thin films have been deposited on p-Si (100) samples by the sol-gel spin coating method. X-Ray diffraction (XRD) and atomic force microscopy (AFM) studies have been done in order to evaluate the structural and morphological properties of the film. The optical properties of the film have been determined by using variable angle ellipsometry. Further, Seebeck measurement of the deposited Cu doped ZnO film leads to positive Seebeck coefficient confirming the p-type conductivity of the sample. The resistivity and acceptor concentration of the film has also been evaluated using four probe measurement system. Pd and Ni metals have been deposited on separate Cu doped ZnO thin film samples using low cost thermal evaporation method to form Schottky contacts. The electrical characterization of the Schottky diode has been performed by semiconductor device analyzer (SDA). Electrical parameters such as barrier height, ideality factor, reverse saturation current and rectification ratio have also been determined for the as-prepared Schottky diode using conventional thermionic emission model and Cheung's method. - Highlights: • Fabrication of sol-gel derived Cu doped ZnO (p-type) Schottky contact proposed. • The p-type Conductivity of the sample confirmed by Seebeck Measurement. • Pd and Ni deposited on Cu doped ZnO film to form Schottky contacts. • Cu doped ZnO expected to emerge as a potential material for thin film solar cells.

Fabrication and characterization of Pd/Cu doped ZnO/Si and Ni/Cu doped ZnO/Si Schottky diodes

International Nuclear Information System (INIS)

Agarwal, Lucky; Singh, Brijesh Kumar; Tripathi, Shweta; Chakrabarti, P.

2016-01-01

In this paper, fabrication and characterization of copper doped ZnO (Cu doped ZnO) based Schottky devices have been reported. Cu doped ZnO thin films have been deposited on p-Si (100) samples by the sol-gel spin coating method. X-Ray diffraction (XRD) and atomic force microscopy (AFM) studies have been done in order to evaluate the structural and morphological properties of the film. The optical properties of the film have been determined by using variable angle ellipsometry. Further, Seebeck measurement of the deposited Cu doped ZnO film leads to positive Seebeck coefficient confirming the p-type conductivity of the sample. The resistivity and acceptor concentration of the film has also been evaluated using four probe measurement system. Pd and Ni metals have been deposited on separate Cu doped ZnO thin film samples using low cost thermal evaporation method to form Schottky contacts. The electrical characterization of the Schottky diode has been performed by semiconductor device analyzer (SDA). Electrical parameters such as barrier height, ideality factor, reverse saturation current and rectification ratio have also been determined for the as-prepared Schottky diode using conventional thermionic emission model and Cheung's method. - Highlights: • Fabrication of sol-gel derived Cu doped ZnO (p-type) Schottky contact proposed. • The p-type Conductivity of the sample confirmed by Seebeck Measurement. • Pd and Ni deposited on Cu doped ZnO film to form Schottky contacts. • Cu doped ZnO expected to emerge as a potential material for thin film solar cells.

Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

Directory of Open Access Journals (Sweden)

Nam-Hee Park

2015-07-01

Full Text Available To provide a convenient and practical synthesis process for metal ion doping on the surface of nanoparticles in an assembled nanostructure, core-shell-structured La-doped SrTiO3 nanocubes with a Nb-doped surface layer were synthesized via a rapid synthesis combining a rapid sol-precipitation and hydrothermal process. The La-doped SrTiO3 nanocubes were formed at room temperature by a rapid dissolution of NaOH pellets during the rapid sol-precipitation process, and the Nb-doped surface (shell along with Nb-rich edges formed on the core nanocubes via the hydrothermal process. The formation mechanism of the core-shell-structured nanocubes and their shape evolution as a function of the Nb doping level were investigated. The synthesized core-shell-structured nanocubes could be arranged face-to-face on a SiO2/Si substrate by a slow evaporation process, and this nanostructured 10 μm thick thin film showed a smooth surface.

The world anti-doping code : a South African perspective : research ...

African Journals Online (AJOL)

During February 2003 the World Anti-Doping Agency adopted the World-Anti Doping Code in Copenhagen in an effort to create and independent anti-doping body and to co-ordinate the harmonisation of doping regulations. The Code encompasses the principles around which the anti-doping effort in sport will revolve in ...

Asymmetrically doped one-dimensional trans-polymers

International Nuclear Information System (INIS)

Caldas, Heron

2009-01-01

More than 30 years ago [H. Shirakawa, E.J. Louis, A.G. MacDiarmid, C.K. Chiang, A.J. Heeger, J. Chem. Soc. Chem. Comm. 578 (1977); S. Etemad, A.J. Heeger, Ann. Rev. Phys. Chem. 33 (1982) 443] it was discovered that doped trans-polyacetylene (CH) x , a one-dimensional (1D) conjugated polymer, exhibits electrical conductivity. In this work we show that an asymmetrically doped 1D trans-polymer has non-conventional properties, as compared to symmetrically doped systems. Depending on the level of asymmetry between the chemical potentials of the two involved fermionic species, the polymer can be in a partially or fully spin polarized state. Some possible experimental consequences of doped 1D trans-polymers used as 1D organic polarized conductors are discussed.

Hydrogen storage capacity of lithium-doped KOH activated carbons

International Nuclear Information System (INIS)

Minoda, Ai; Oshima, Shinji; Iki, Hideshi; Akiba, Etsuo

2014-01-01

Highlights: • The hydrogen adsorption of lithium-doped KOH activated carbons has been studied. • Lithium doping improves their hydrogen adsorption affinity. • Lithium doping is more effective for materials with micropores of 0.8 nm or smaller. • Lithium reagent can alter the pore structure, depending on the raw material. • Optimizing the pore size and functional group is needed for better hydrogen uptake. - Abstract: The authors have studied the hydrogen adsorption performance of several types of lithium-doped KOH activated carbons. In the case of activated cokes, lithium doping improves their hydrogen adsorption affinity from 5.02 kg/m 3 to 5.86 kg/m 3 at 303 K. Hydrogen adsorption density increases by around 17% after lithium doping, likely due to the fact that lithium doping is more effective for materials with micropores of 0.8 nm or smaller. The effects of lithium on hydrogen storage capacity vary depending on the raw material, because the lithium reagent can react with the material and alter the pore structure, indicating that lithium doping has the effect of plugging or filling the micropores and changing the structures of functional groups, resulting in the formation of mesopores. Despite an observed decrease in hydrogen uptake, lithium doping was found to improve hydrogen adsorption affinity. Lithium doping increases hydrogen uptake by optimizing the pore size and functional group composition

Light-induced enhancement of the minority carrier lifetime in boron-doped Czochralski silicon passivated by doped silicon nitride

International Nuclear Information System (INIS)

Wang, Hongzhe; Chen, Chao; Pan, Miao; Sun, Yiling; Yang, Xi

2015-01-01

Graphical abstract: - Highlights: • The phosphorus-doped SiN x with negative fixed charge was deposited by PECVD. • The increase of lifetime was observed on P-doped SiN x passivated Si under illumination. • The enhancement of lifetime was caused by the increase of negative fixed charges. - Abstract: This study reports a doubling of the effective minority carrier lifetime under light soaking conditions, observed in a boron-doped p-type Czochralski grown silicon wafer passivated by a phosphorus-doped silicon nitride thin film. The analysis of capacitance–voltage curves revealed that the fixed charge in this phosphorus-doped silicon nitride film was negative, which was unlike the well-known positive fixed charges observed in traditional undoped silicon nitride. The analysis results revealed that the enhancement phenomenon of minority carrier lifetime was caused by the abrupt increase in the density of negative fixed charge (from 7.2 × 10 11 to 1.2 × 10 12 cm −2 ) after light soaking.

In situ observation of triple junction motion during recovery of heavily deformed aluminum

DEFF Research Database (Denmark)

Yu, Tianbo; Hughes, Darcy A.; Hansen, Niels

2015-01-01

-junctions are pinned by deformation-induced interconnecting and lamellar boundaries, which slow down the recovery process and lead to a stop-go migration pattern. This pinning mechanism stabilizes the deformation microstructure, i.e. the structure is stabilized by balancing the driving and pinning forces controlling......Microstructural evolution during in situ annealing of heavily cold-rolled aluminum has been studied by transmission electron microscopy, confirming that an important recovery mechanism is migration of triple junctions formed by three lamellar boundaries (Y-junctions). The migrating Y...

Nice Guys Finish Last: Are People with Higher Tax Morale Taxed more Heavily?

OpenAIRE

Philipp Doerrenberg; Denvil Duncan; Clemens Fuest; Andreas Peichl

2012-01-01

This paper is the first to provide evidence of efficient taxation of groups with heterogeneous levels of 'tax morale'. We set up an optimal income tax model where high tax morale implies a high subjective cost of evading taxes. The model predicts that 'nice guys finish last': groups with higher tax morale will be taxed more heavily, simply because taxing them is less costly. Based on unique cross-country micro data and an IV approach to rule out reverse causality, we find empirical support fo...

Proton-transfer doping of polyacetylene

Energy Technology Data Exchange (ETDEWEB)

Tolbert, L.M.; Schomaker, J.A. (School of Chemistry and Biochemistry, Georgia Inst. of Tech., Atlanta (USA))

1991-04-30

Exhaustive deprotonation of films of poly(acetylene-co-1,3-butadiene) (PAB) fails to produce a conductive film. In contrast, deprotonation of segmented polyacetylene (SPA) produces a conductive material with similar characteristics to n-doped polyacetylene. Thus the feasibility of a proton-transfer approach to doping of polyacetylene has been demonstrated. (orig.).

Neutron transmutation doped Ge bolometers

Science.gov (United States)

Haller, E. E.; Kreysa, E.; Palaio, N. P.; Richards, P. L.; Rodder, M.

1983-01-01

Some conclusions reached are as follow. Neutron Transmutation Doping (NTD) of high quality Ge single crystals provides perfect control of doping concentration and uniformity. The resistivity can be tailored to any given bolometer operating temperature down to 0.1 K and probably lower. The excellent uniformity is advantaged for detector array development.

Review on dielectric properties of rare earth doped barium titanate

International Nuclear Information System (INIS)

Ismail, Fatin Adila; Osman, Rozana Aina Maulat; Idris, Mohd Sobri

2016-01-01

Rare earth doped Barium Titanate (BaTiO_3) were studied due to high permittivity, excellent electrical properties and have wide usage in various applications. This paper reviewed on the electrical properties of RE doped BaTiO_3 (RE: Lanthanum (La), Erbium (Er), Samarium (Sm), Neodymium (Nd), Cerium (Ce)), processing method, phase transition occurred and solid solution range for complete study. Most of the RE doped BaTiO_3 downshifted the Curie temperature (T_C). Transition temperature also known as Curie temperature, T_C where the ceramics had a transition from ferroelectric to a paraelectric phase. In this review, the dielectric constant of La-doped BaTiO_3, Er-doped BaTiO_3, Sm-doped BaTiO_3, Nd-doped BaTiO_3 and Ce-doped BaTiO_3 had been proved to increase and the transition temperature or also known as T_C also lowered down to room temperature as for all the RE doped BaTiO_3 except for Er-doped BaTiO_3.

Two and four photon absorption and nonlinear refraction in undoped, chromium doped and copper doped ZnS quantum dots

Science.gov (United States)

Sharma, Dimple; Malik, B. P.; Gaur, Arun

2015-12-01

The ZnS quantum dots (QDs) with Cr and Cu doping were synthesized by chemical co-precipitation method. The nanostructures of the prepared undoped and doped ZnS QDs were characterized by UV-vis spectroscopy, Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The sizes of QDs were found to be within 3-5 nm range. The nonlinear parameters viz. Two photon absorption coefficient (β2), nonlinear refractive index (n2), third order nonlinear susceptibility (χ3) at wavelength 532 nm and Four photon absorption coefficient (β4) at wavelength 1064 nm have been calculated by Z-scan technique using nanosecond Nd:YAG laser in undoped, Cr doped and Cu doped ZnS QDs. Higher values of nonlinear parameters for doped ZnS infer that they are potential material for the development of photonics devices and sensor protection applications.

Cobalt doped proangiogenic hydroxyapatite for bone tissue engineering application

Energy Technology Data Exchange (ETDEWEB)

Kulanthaivel, Senthilguru [Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India); Roy, Bibhas [Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302 (India); Agarwal, Tarun [Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India); Giri, Supratim [Department of Chemistry, National Institute of Technology, Rourkela, Odisha 769008 (India); Pramanik, Krishna; Pal, Kunal; Ray, Sirsendu S. [Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India); Maiti, Tapas K. [Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302 (India); Banerjee, Indranil, E-mail: indraniliit@gmail.com [Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India)

2016-01-01

ABSTRACT: The present study delineates the synthesis and characterization of cobalt doped proangiogenic–osteogenic hydroxyapatite. Hydroxyapatite samples, doped with varying concentrations of bivalent cobalt (Co{sup 2+}) were prepared by the ammoniacal precipitation method and the extent of doping was measured by ICP–OES. The crystalline structure of the doped hydroxyapatite samples was confirmed by XRD and FTIR studies. Analysis pertaining to the effect of doped hydroxyapatite on cell cycle progression and proliferation of MG-63 cells revealed that the doping of cobalt supported the cell viability and proliferation up to a threshold limit. Furthermore, such level of doping also induced differentiation of the bone cells, which was evident from the higher expression of differentiation markers (Runx2 and Osterix) and better nodule formation (SEM study). Western blot analysis in conjugation with ELISA study confirmed that the doped HAp samples significantly increased the expression of HIF-1α and VEGF in MG-63 cells. The analysis described here confirms the proangiogenic–osteogenic properties of the cobalt doped hydroxyapatite and indicates its potential application in bone tissue engineering. - Highlights: • Cobalt (Co{sup +2}) doped hydroxyapatite (Co-HAp) can be prepared by the wet chemical method. • The concentration of Co{sup +2} influences the physico-chemical properties of HAp. • Co-HAp was found to be biocompatible and osteogenic. • Co-HAp enhanced cellular VEGF secretion through HIF-1α stabilization. • The optimum biological performance of Co-HAp was achieved for 0.33% (w/w) Co{sup +2} doping.

Density functional theory calculations on the adsorption of formaldehyde and other harmful gases on pure, Ti-doped, or N-doped graphene sheets

International Nuclear Information System (INIS)

Zhang, Hong-ping; Luo, Xue-gang; Lin, Xiao-yang; Lu, Xiong; Leng, Yang; Song, Hong-tao

2013-01-01

Understanding the interaction mechanisms of CO, NO, SO 2 , and HCHO with graphene are important in developing graphene-based sensors for gas detection and removal. In this study, the effects of doped Ti or N atom on the interaction of these gases with graphene were investigated by density functional theory calculations. Analyses of adsorption energy, electron density difference, and density of states indicated that the doped Ti atom could greatly improve the interaction of gas molecules with graphene. The Ti-doped graphene sheet demonstrated selective gas absorption. The order of interaction between the gas molecules and the Ti-doped graphene sheet was as follows: SO 2 > NO > HCHO > CO. By contrast, the N-doped graphene sheet did not exhibit apparent selective gas absorption. These results imply that the Ti-doped graphene sheet is more effective than the N-doped graphene sheet in detecting and removing gas molecules because of its high selectivity.

Density functional theory calculations on the adsorption of formaldehyde and other harmful gases on pure, Ti-doped, or N-doped graphene sheets

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hong-ping, E-mail: zhp1006@126.com [Engineering Research Center of Biomass Materials, Ministry of Education, School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Luo, Xue-gang, E-mail: lxg@swust.edu.cn [Engineering Research Center of Biomass Materials, Ministry of Education, School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Lin, Xiao-yang, E-mail: xylin-2004@163.com [Engineering Research Center of Biomass Materials, Ministry of Education, School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Lu, Xiong, E-mail: luxiong_2004@163.com [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan (China); Leng, Yang, E-mail: meleng@ust.hk [Department of Mechanical Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong (China); Song, Hong-tao, E-mail: yinyishushengsht@163.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

2013-10-15

Understanding the interaction mechanisms of CO, NO, SO{sub 2}, and HCHO with graphene are important in developing graphene-based sensors for gas detection and removal. In this study, the effects of doped Ti or N atom on the interaction of these gases with graphene were investigated by density functional theory calculations. Analyses of adsorption energy, electron density difference, and density of states indicated that the doped Ti atom could greatly improve the interaction of gas molecules with graphene. The Ti-doped graphene sheet demonstrated selective gas absorption. The order of interaction between the gas molecules and the Ti-doped graphene sheet was as follows: SO{sub 2} > NO > HCHO > CO. By contrast, the N-doped graphene sheet did not exhibit apparent selective gas absorption. These results imply that the Ti-doped graphene sheet is more effective than the N-doped graphene sheet in detecting and removing gas molecules because of its high selectivity.

Synthesis and characterization of Gd-doped magnetite nanoparticles

International Nuclear Information System (INIS)

Zhang, Honghu; Malik, Vikash; Mallapragada, Surya; Akinc, Mufit

2017-01-01

Synthesis of magnetite nanoparticles has attracted increasing interest due to their importance in biomedical and technological applications. Tunable magnetic properties of magnetite nanoparticles to meet specific requirements will greatly expand the spectrum of applications. Tremendous efforts have been devoted to studying and controlling the size, shape and magnetic properties of magnetite nanoparticles. Here we investigate gadolinium (Gd) doping to influence the growth process as well as magnetic properties of magnetite nanocrystals via a simple co-precipitation method under mild conditions in aqueous media. Gd doping was found to affect the growth process leading to synthesis of controllable particle sizes under the conditions tested (0–10 at% Gd"3"+). Typically, undoped and 5 at% Gd-doped magnetite nanoparticles were found to have crystal sizes of about 18 and 44 nm, respectively, supported by X-ray diffraction and transmission electron microscopy. Our results showed that Gd-doped nanoparticles retained the magnetite crystal structure, with Gd"3"+ randomly incorporated in the crystal lattice, probably in the octahedral sites. The composition of 5 at% Gd-doped magnetite was Fe_(_3_−_x_)Gd_xO_4 (x=0.085±0.002), as determined by inductively coupled plasma mass spectrometry. 5 at% Gd-doped nanoparticles exhibited ferrimagnetic properties with small coercivity (~65 Oe) and slightly decreased magnetization at 260 K in contrast to the undoped, superparamagnetic magnetite nanoparticles. Templation by the bacterial biomineralization protein Mms6 did not appear to affect the growth of the Gd-doped magnetite particles synthesized by this method. - Highlights: • Gd-doped magnetite nanoparticles are synthesized via aqueous co-precipitation method under mild conditions. • Gd doping affects growth of magnetite nanoparticles leading to tunable particle size. • Gd-doped magnetite nanoparticles exhibit ferrimagnetic properties.

Porous allograft bone scaffolds: doping with strontium.

Directory of Open Access Journals (Sweden)

Yantao Zhao

Full Text Available Strontium (Sr can promote the process of bone formation. To improve bioactivity, porous allograft bone scaffolds (ABS were doped with Sr and the mechanical strength and bioactivity of the scaffolds were evaluated. Sr-doped ABS were prepared using the ion exchange method. The density and distribution of Sr in bone scaffolds were investigated by inductively coupled plasma optical emission spectrometry (ICP-OES, X-ray photoelectron spectroscopy (XPS, and energy-dispersive X-ray spectroscopy (EDS. Controlled release of strontium ions was measured and mechanical strength was evaluated by a compressive strength test. The bioactivity of Sr-doped ABS was investigated by a simulated body fluid (SBF assay, cytotoxicity testing, and an in vivo implantation experiment. The Sr molar concentration [Sr/(Sr+Ca] in ABS surpassed 5% and Sr was distributed nearly evenly. XPS analyses suggest that Sr combined with oxygen and carbonate radicals. Released Sr ions were detected in the immersion solution at higher concentration than calcium ions until day 30. The compressive strength of the Sr-doped ABS did not change significantly. The bioactivity of Sr-doped material, as measured by the in vitro SBF immersion method, was superior to that of the Sr-free freeze-dried bone and the Sr-doped material did not show cytotoxicity compared with Sr-free culture medium. The rate of bone mineral deposition for Sr-doped ABS was faster than that of the control at 4 weeks (3.28 ± 0.23 µm/day vs. 2.60 ± 0.20 µm/day; p<0.05. Sr can be evenly doped into porous ABS at relevant concentrations to create highly active bone substitutes.

Synthesis of Antimony Doped Amorphous Carbon Films

Science.gov (United States)

Okuyama, H.; Takashima, M.; Akasaka, H.; Ohtake, N.

2013-06-01

We report the effects of antimony (Sb) doping on the electrical and optical properties of amorphous carbon (a-C:H) films grown on silicon and copper substrates by magnetron sputtering deposition. For film deposition, the mixture targets fabricated from carbon and antimony powders was used. The atomic concentration of carbon, hydrogen, and antimony, in the film deposited from the 1.0 mol% Sb containing target were 81, 17, 2 at.%, respectively. These elements were homogeneously distributed in the film. On the structural effect, the average continuous sp2 carbon bonding networks decreased with Sb concentration increasing, and defects in the films were increased with the Sb incorporation because atomic radius of Sb atoms is twice larger size than that of carbon. The optical gap and the electrical resistivity were carried out before and after the Sb doping. The results show that optical gap dropped from 3.15 to 3.04 eV corresponding to non-doping to Sb-doping conditions, respectively. The electrical resistivity reduced from 10.5 to 1.0 MΩm by the Sb doping. These results suggest the doping level was newly formed in the forbidden band.

Synthesis of Antimony Doped Amorphous Carbon Films

International Nuclear Information System (INIS)

Okuyama, H; Takashima, M; Akasaka, H; Ohtake, N

2013-01-01

We report the effects of antimony (Sb) doping on the electrical and optical properties of amorphous carbon (a-C:H) films grown on silicon and copper substrates by magnetron sputtering deposition. For film deposition, the mixture targets fabricated from carbon and antimony powders was used. The atomic concentration of carbon, hydrogen, and antimony, in the film deposited from the 1.0 mol% Sb containing target were 81, 17, 2 at.%, respectively. These elements were homogeneously distributed in the film. On the structural effect, the average continuous sp 2 carbon bonding networks decreased with Sb concentration increasing, and defects in the films were increased with the Sb incorporation because atomic radius of Sb atoms is twice larger size than that of carbon. The optical gap and the electrical resistivity were carried out before and after the Sb doping. The results show that optical gap dropped from 3.15 to 3.04 eV corresponding to non-doping to Sb-doping conditions, respectively. The electrical resistivity reduced from 10.5 to 1.0 MΩm by the Sb doping. These results suggest the doping level was newly formed in the forbidden band.

Doping w sporcie jako problem etyczno-społeczny = Doping in sport as a problem ethical and social

Directory of Open Access Journals (Sweden)

Aleksandra Lewandowska

2016-07-01

  Streszczenie: Celem pracy jest omówienie zagadnienia dopingu stosowanego w sporcie w kontekście prawdopodobnych konsekwencji społecznych związanych z jego stosowaniem, jak również na płaszczyźnie biomedycznej związanej z dynamicznym rozwojem technologii biomedycznych w obszarze wzmocnień ludzkiego organizmu. Poza analizą zagadnienia jakości „zdopingowanego sportu” w perspektywie rozstrzygnięć bioetycznych w tekście przywołane zostały statystyki ukazujące zastosowanie dopingu w sporcie, w ujęciu tak czasowym, jak również przestrzennym.   Słowa kluczowe: sport, doping, doping genetyczny, etyka w sporcie, jakość w sporcie.   Abstract: The article presents the issues of doping in sport used in the context of possible social consequences associated with its use, as well as at the level of biomedical related to the rapid development of biomedical technologies in area of human  body enhancement. In addition to the analysis of quality issues "sport enhancement" in the perspective of bioethical resolving, in the text refers to statistics showing the use of doping in sport, in terms both time as well as spatial.   Key words: sports, doping, gene doping, ethics in sport, quality in sport.

Copper doped borate dosimeters revisited

International Nuclear Information System (INIS)

Alajerami, Y.S.M.; Hashim, S.; Ghoshal, S.K.; Bradley, D.A.; Mhareb, M.; Saleh, M.A.

2014-01-01

We render a panoramic overview on copper (Cu) doped borate dosimeters. Preparing a dosimeter by mixing specific materials with precise weights and methods is a never-ending quest. The recommended composition is highly decisive for accurate estimation of the absorbed dose, prediction of the biological outcome, determination of the treatment dose for radiation therapy and facilitation of personal monitoring. Based on these principles, the proposed dosimeter must cover a series of dosimetric properties to realize the exact results and assessment. The doped borate dosimeters indeed demonstrate attractive thermoluminescence (TL) features. Several dedicated efforts are attempted to improve the luminescence properties by doping various transition metals or rare-earth elements. The Cu ion being one of the preferred activators shows excellent TL properties as revealed via detail comparison with other dosimeters. Two oxide states of Cu (Cu + and Cu ++ ) with reasonable atomic number allow easy interaction with boron network. Interestingly, the intrinsic luminescent centers of borate lattice are in cross linked with that of Cu + ions. Thus, the activation of borate dosimeter with Cu ions for the enhancement of the TL sensitivity is recognized. These dosimeters reveal similar glow curves as the standard TLD-100 (LiF:Mg,Ti) one irrespective of the use of modifiers and synthesis techniques. They display high sensitivity, low fading, dose response linearity over wide range and practical minimum detectable dose. Furthermore, the effective atomic number being the most beneficial aspect (equivalent to that of human tissue) of borate dosimeters do not show any change due to Cu ion activations. The past development, major challenges, excitement, applications, recent progress and the future promises of Cu doped borate TL dosimeters are highlighted. - Highlights: • The manuscript gives a panoramic overview on copper doped borate dosimeters. • Cu ions activated technique in borate

Optical method for the screening of doping substances

Science.gov (United States)

Lademann, J.; Shevtsova, J.; Patzelt, A.; Richter, H.; Gladkowa, N. D.; Gelikonov, V. M.; Gonchukov, S. A.; Sterry, W.; Blume-Peytavi, U.

2008-12-01

During the last years, an increased misuse of doping substances in sport has been observed. The action of doping substances characterized by the stimulation of blood flow and metabolic processes is also reflected in the hair structure. In the present study it was demonstrated that optical coherent tomography is well suited for the analysis of hair parameters influenced by doping. Analyzing 20 patients, systemically treated with steroids which also represent doping substances, it was found that in all cases a significant increase in the cross-section of the hairs could be detected. The results obtained in the study are not only important for the screening of doping substances but also for medical diagnostics and control of compliance of patients.

Optical method for the screening of doping substances

International Nuclear Information System (INIS)

Lademann, J; Patzelt, A; Richter, H; Sterry, W; Shevtsova, J; Gladkowa, N D; Gelikonov, V M; Gonchukov, S A; Blume-Peytavi, U

2008-01-01

During the last years, an increased misuse of doping substances in sport has been observed. The action of doping substances characterized by the stimulation of blood flow and metabolic processes is also reflected in the hair structure. In the present study it was demonstrated that optical coherent tomography is well suited for the analysis of hair parameters influenced by doping. Analyzing 20 patients, systemically treated with steroids which also represent doping substances, it was found that in all cases a significant increase in the cross-section of the hairs could be detected. The results obtained in the study are not only important for the screening of doping substances but also for medical diagnostics and control of compliance of patients

[Gene doping: gene transfer and possible molecular detection].

Science.gov (United States)

Argüelles, Carlos Francisco; Hernández-Zamora, Edgar

2007-01-01

The use of illegal substances in sports to enhance athletic performance during competition has caused international sports organizations such as the COI and WADA to take anti doping measures. A new doping method know as gene doping is defined as "the non-therapeutic use of genes, genetic elements and/or cells that have the capacity to enhance athletic performance". However, gene doping in sports is not easily identified and can cause serious consequences. Molecular biology techniques are needed in order to distinguish the difference between a "normal" and an "altered" genome. Further, we need to develop new analytic methods and biological molecular techniques in anti-doping laboratories, and design programs that avoid the non therapeutic use of genes.

Large-area uniform electron doping of graphene by Ag nanofilm

Directory of Open Access Journals (Sweden)

Xiaopeng Guo

2017-04-01

Full Text Available Graphene has attracted much attention at various research fields due to its unique optical, electronic and mechanical properties. Up to now, graphene has not been widely used in optoelectronic fields due to the lack of large-area uniform doped graphene (n-doped and p-doped with smooth surface. Therefore, it is rather desired to develop some effective doping methods to extend graphene to optoelectronics. Here we developed a novel doping method to prepare large-area (> centimeter scale uniform doped graphene film with a nanoscale roughness(RMS roughness ∼1.4 nm, the method (nano-metal film doping method is simple but effective. Using this method electron doping (electron-injection may be easily realized by the simple thermal deposition of Ag nano-film on a transferred CVD graphene. The doping effectiveness has been proved by Raman spectroscopy and spectroscopic ellipsometry. Importantly, our method sheds light on some potential applications of graphene in optoelectronic devices such as photodetectors, LEDs, phototransistors, solar cells, lasers etc.

GENES IN SPORT AND DOPING

Directory of Open Access Journals (Sweden)

Andrzej Pokrywka

2013-06-01

Full Text Available Genes control biological processes such as muscle production of energy, mitochondria biogenesis, bone formation erythropoiesis, angiogenesis, vasodilation, neurogenesis, etc. DNA profiling for athletes reveals genetic variations that may be associated with endurance ability, muscle performance and power exercise, tendon susceptibility to injuries and psychological aptitude. Already, over 200 genes relating to physical performance have been identified by several research groups. Athletes’ genotyping is developing as a tool for the formulation of personalized training and nutritional programmes to optimize sport training as well as for the prediction of exercise-related injuries. On the other hand, development of molecular technology and gene therapy creates a risk of non-therapeutic use of cells, genes and genetic elements to improve athletic performance. Therefore, the World Anti-Doping Agency decided to include prohibition of gene doping within their World Anti-Doping Code in 2003. In this review article, we will provide a current overview of genes for use in athletes’ genotyping and gene doping possibilities, including their development and detection techniques.

N-doping of organic semiconductors by bis-metallosandwich compounds

Science.gov (United States)

Barlow, Stephen; Qi, Yabing; Kahn, Antoine; Marder, Seth; Kim, Sang Bok; Mohapatra, Swagat K.; Guo, Song

2016-01-05

The various inventions disclosed, described, and/or claimed herein relate to the field of methods for n-doping organic semiconductors with certain bis-metallosandwich compounds, the doped compositions produced, and the uses of the doped compositions in organic electronic devices. Metals can be manganese, rhenium, iron, ruthenium, osmium, rhodium, or iridium. Stable and efficient doping can be achieved.

Thirteen years of the fight against doping in figures.

Science.gov (United States)

Aguilar, Millán; Muñoz-Guerra, Jesús; Plata, María Del Mar; Del Coso, Juan

2017-06-01

Every year, the World Anti-Doping Agency (WADA) publishes the main statistics reported by the accredited laboratories, which provide very valuable information for assessing changes in the patterns of doping in sports over time. Using the information provided since 2003 as the basis for the analysis, the evolution of doping/anti-doping figures over the last decade can be examined in reasonable detail, at least in reference to samples analyzed and categories of substances more commonly found in athletes' samples. This brief analysis of the WADA statistical reports leads us to the following outcomes: the increase in anti-doping pressure from 2003 to 2015, as evidenced by increased numbers of samples analyzed and banned substances, has not directly produced a higher frequency of adverse/atypical findings. Although this could be interpreted as steady state in the capacity to detect doping through this whole period, it also resulted in a significant increase in the absolute number of samples catalogued as doping (from 2247 in 2003 to 5912 in 2015). Anabolic agents have been the most common doping substances detected in all statistics reports while the remaining groups of substances are much less frequently found in doping control samples. Given that one might have expected the enhancement of the anti-doping programme led by WADA over this last decade to have increased the percentage of adverse/atypical findings, the fact that it did not might indicate the need to take another step in sampling strategies, such as 'more intelligent testing' based on the differences in the prevalence of doping substances among sports. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

The fight against fitness doping in sports clubs

DEFF Research Database (Denmark)

Thualagant, Nicole; Pfister, Gertrud Ursula

2012-01-01

This article focuses on the anti-doping policies led in Danish fitness centers in a sport for all context. Fitness, an ever growing training form is gaining in popularity and has in this context been adopted as a training activity by DGI, one of the leading sports for all organization in Denmark....... As a result of this gain in popularity, fitness activities are not only offered in commercial fitness centers but also in fitness centers attached to sport for all clubs. This development has emancipated a focus on doping and thereby in the establishing of anti-doping policies in sport for all clubs. Denmark...... is one of the few countries who illegalizes doping in fitness centers and who tests its members for doping. This article contributes with a discussion concerning the challenges, DGI, as a sport for all organization encounters in relation to the anti-doping policies and its objectives of fostering health...

Doping dependence of Meissner effect in cuprate superconductors

International Nuclear Information System (INIS)

Feng Shiping; Huang Zheyu; Zhao Huaisong

2010-01-01

Within the t-t'-J model, the doping dependence of the Meissner effect in cuprate superconductors is studied based on the kinetic energy driven superconducting mechanism. Following the linear response theory, it is shown that the electromagnetic response consists of two parts, the diamagnetic current and the paramagnetic current, which exactly cancels the diamagnetic term in the normal state, and then the Meissner effect is obtained for all the temperature T ≤ T c throughout the superconducting dome. By considering the two-dimensional geometry of cuprate superconductors within the specular reflection model, the main features of the doping and temperature dependence of the local magnetic field profile, the magnetic field penetration depth, and the superfluid density observed on cuprate superconductors are well reproduced. In particular, it is shown that in analogy to the domelike shape of the doping dependent superconducting transition temperature, the maximal superfluid density occurs around the critical doping δ ∼ 0.195, and then decreases in both lower doped and higher doped regimes.

Genetic algorithm based approach to investigate doped metal oxide materials: Application to lanthanide-doped ceria

Science.gov (United States)

Hooper, James; Ismail, Arif; Giorgi, Javier B.; Woo, Tom K.

2010-06-01

A genetic algorithm (GA)-inspired method to effectively map out low-energy configurations of doped metal oxide materials is presented. Specialized mating and mutation operations that do not alter the identity of the parent metal oxide have been incorporated to efficiently sample the metal dopant and oxygen vacancy sites. The search algorithms have been tested on lanthanide-doped ceria (L=Sm,Gd,Lu) with various dopant concentrations. Using both classical and first-principles density-functional-theory (DFT) potentials, we have shown the methodology reproduces the results of recent systematic searches of doped ceria at low concentrations (3.2% L2O3 ) and identifies low-energy structures of concentrated samarium-doped ceria (3.8% and 6.6% L2O3 ) which relate to the experimental and theoretical findings published thus far. We introduce a tandem classical/DFT GA algorithm in which an inexpensive classical potential is first used to generate a fit gene pool of structures to enhance the overall efficiency of the computationally demanding DFT-based GA search.

Doping and thrombosis in sports.

Science.gov (United States)

Lippi, Giuseppe; Banfi, Giuseppe

2011-11-01

Historically, humans have long sought to enhance their "athletic" performance to increase body weight, aggressiveness, mental concentration and physical strength, contextually reducing fatigue, pain, and improving recovery. Although regular training is the mainstay for achieving these targets, the ancillary use of ergogenic aids has become commonplace in all sports. The demarcation between ergogenic aids and doping substances or practices is continuously challenging and mostly based on perceptions regarding the corruption of the fairness of competition and the potential side effects or adverse events arising from the use of otherwise unnecessary ergogenic substances. A kaleidoscope of side effects has been associated with the use of doping agents, including behavioral, skeletal, endocrinologic, metabolic, hemodynamic, and cardiovascular imbalances. Among the various doping substances, the most striking association with thrombotic complications has been reported for androgenic anabolic steroids (i.e., cardiomyopathy, fatal and nonfatal arrhythmias, myocardial infarction [MI], intracardiac thrombosis, stroke, venous thromboembolism [VTE], limb arterial thrombosis, branch retinal vein occlusion, cerebral venous sinus thrombosis) and blood boosting (i.e., VTE and MI, especially for epoetin and analogs). The potential thrombotic complication arising from misuse of other doping agents such as the administration of cortisol, growth hormone, prolactin, cocaine, and platelet-derived preparations is instead speculative or anecdotal at best. The present article provides an overview on the epidemiological association as well as the underlying biochemical and biological mechanisms linking the practice of doping in sports with the development of thrombosis. © Thieme Medical Publishers.

Doped luminescent materials and particle discrimination using same

Science.gov (United States)

Doty, F. Patrick; Allendorf, Mark D; Feng, Patrick L

2014-10-07

Doped luminescent materials are provided for converting excited triplet states to radiative hybrid states. The doped materials may be used to conduct pulse shape discrimination (PSD) using luminescence generated by harvested excited triplet states. The doped materials may also be used to detect particles using spectral shape discrimination (SSD).

Preparation of antimony-doped nanoparticles by hydrothermal method

Institute of Scientific and Technical Information of China (English)

JIANG Ming-xi; YANG Tian-zu; GU Ying-ying; DU Zuo-juan; LIU Jian-ling

2005-01-01

Antimony-doped tin oxide(ATO) nanoparticles were prepared by the mild hydrothermal method at 200 ℃ using sodium stannate, antimony oxide, sodium hydroxide and sulfuric acid as the starting materials. The doped powders were examined by differential thermal analysis(DTA), X-ray diffractometry(XRD) and transmission electron microscopy(TEM). The doping levels of antimony were determined by volumetric method and iodimetry.The results show that antimony is incorporated into the crystal lattice of tin oxide and the doping levels of antimony in the resulting powders are 2.4%, 4.3 % and 5.1 % (molar fraction). The mean particle size of ATO nanoparticles is in the range of 25 - 30 nm. The effects of antimony doping level on the crystalline size and crystallinity were also discussed.

BLOOD DOPING AND RISKS

Directory of Open Access Journals (Sweden)

Goran Vasić

2015-05-01

Full Text Available Doping is the way in which athletes misuse of chemicals and other types of medical interventions (eg, blood replacement, try to get ahead in the results of other athletes or their performance at the expense of their own health. The aim of this work is the analysis of blood doping and the display of negative consequences that this way of increasing capabilities brings. Method: The methodological work is done descriptively. Results: Even in 1972 at the Stockholm Institute for gymnastics and sport, first Dr. Bjorn Ekblom started having blood doping. Taken from the blood, athletes through centifuge separating red blood cells from blood plasma, which is after a month of storage in the fridge, every athlete back into the bloodstream. Tests aerobic capacity thereafter showed that the concerned athletes can run longer on average for 25% of the treadmill than before. Discussion: Blood doping carries with it serious risks, excessive amount of red cells “thickens the blood,” increased hematocrit, which reduces the heart’s ability to pump blood to the periphery. All this makes it difficult for blood to flow through blood vessels, and there is a great danger that comes to a halt in the circulation, which can cause cardiac arrest, stroke, pulmonary edema, and other complications that can be fatal.

Characteristics of Mg-doped and In-Mg co-doped p-type GaN epitaxial layers grown by metal organic chemical vapour deposition

International Nuclear Information System (INIS)

Chung, S J; Lee, Y S; Suh, E-K; Senthil Kumar, M; An, M H

2010-01-01

Mg-doped and In-Mg co-doped p-type GaN epilayers were grown using the metal organic chemical vapour deposition technique. The effect of In co-doping on the physical properties of p-GaN layer was examined by high resolution x-ray diffraction (HRXRD), transmission electron microscopy (TEM), Hall effect, photoluminescence (PL) and persistent photoconductivity (PPC) at room temperature. An improved crystalline quality and a reduction in threading dislocation density are evidenced upon In doping in p-GaN from HRXRD and TEM images. Hole conductivity, mobility and carrier density also significantly improved by In co-doping. PL studies of the In-Mg co-doped sample revealed that the peak position is blue shifted to 3.2 eV from 2.95 eV of conventional p-GaN and the PL intensity is increased by about 25%. In addition, In co-doping significantly reduced the PPC effect in p-type GaN layers. The improved electrical and optical properties are believed to be associated with the active participation of isolated Mg impurities.

The electrical properties of a strongly disordered system based on lightly doped germanium compensated by disordered regions

International Nuclear Information System (INIS)

Evseev, V.A.; Konopleva, R.F.; Yuferev, A.A.

1976-01-01

A study was made of lightly doped (Nsub(Sb) approximately 10 15 cm -3 ) n-Ge, heavily compensated (K = Nsub(A)/N sub(D) approximately 1) by fast neutrons from a reactor. Irradiation is shown to produce, near n-p conversion (annealing has the same effect near p-n conversion), a random relief of electrostatic potential which is caused by the overlap of the space-charge regions surrounding disordered regions (DR). the random potential field results in a spatial 'bending' of the whole band spectrum of germanium, similar to the way it is observed in amorphous semiconductors because of their disorder. Experiments show the conduction in the DR overlap region to be of an activated nature, associated with the ejection of carriers to the corresponding 'percolation' levels. The activation energy of such conduction varies with the degree of compensation. The shift of the Fermi level depends on the degree of compensation here in a much more sensitive way than in the case of compensation by chemical impurities. The properties of Ge obtained by DR overlap and by compensation with chemical impurities are compared. A superlinear I-V characteristic producing the switching effect is observed in strong electric fields (E approximately 10 3 V cm -1 ). A suggestion is made that a study of disordered systems, based on lightly doped germanium which is compensated with DRs produced by high-energy particles, should both help to obtain new information on the parameters of the DRs proper and help to simulate the properties of the amorphous semiconductors. (author)

Overcoming doping limits in MOVPE grown n-doped InP for plasmonic applications

DEFF Research Database (Denmark)

Panah, Mohammad Esmail Aryaee; Xiao, Sanshui; Lavrinenko, Andrei

2015-01-01

Effect of the growth parameters on carrier concentration in MOVPE grown silicon-doped InP is studied. The dopant flow, V/III ratio and substrate temperature are optimized by considering the origin of the doping limits. In addition, two different group V precursors, namely PH3 and TBP, are compare......×1019cm-3 is achieved. Optical properties of the samples are investigated by Fourier transform infrared reflection (FTIR) spectroscopy and are fitted by a Drude-Lorentz function....

Electrical properties of phosphorene systems doped with fourth-period elements

Science.gov (United States)

Wang, Ke; Wang, Hai; Zhang, Min; Liu, Yan; Zhao, Wei

2018-05-01

In this work, we use a first-principles calculation to investigate the structure, binding energies, and electrical properties of monolayer phosphorene systems doped with fourth-period main group elements at a doping concentration of 6.25%. The calculation results reveal that, although large deformations exist, all doped systems are stable and non-spin polarized. In addition, the Ca, Se, and Br atoms are electron acceptors in the doped systems, whereas the Ga, Ge and As atoms are donors. Thus, there is an ionic bonding character between the dopants and neighboring phosphorus atoms in the Ca-, Ga-, Ge-, As-, Se-, and Br-doped systems. From band structures, we find that the K-, Ga-, As-, and Br-doped systems present semiconducting states with indirect gaps, whereas the Ca-, Ge-, and Se-doped systems have metallic states. We conclude that the metallicity of a phosphorene system doped with main-group elements depends on the number of valence electrons of the dopant. This investigation provides directions for manipulating the electrical properties of phosphorene by substitutional doping, which would broaden its possible applications in optoelectronics.

The nature of the torus in the heavily obscured AGN Markarian 3: an X-ray study

DEFF Research Database (Denmark)

Guainazzi, M.; Risaliti, G.; Awaki, H.

2016-01-01

In this paper, we report the results of an X-ray monitoring campaign on the heavily obscured Seyfert galaxy, Markarian 3, carried out between the fall of 2014 and the spring of 2015 with NuSTAR, Suzaku and XMM–Newton. The hard X-ray spectrum of Markarian 3 is variable on all the time-scales probe...

Detection of EPO gene doping in blood.

Science.gov (United States)

Neuberger, Elmo W I; Jurkiewicz, Magdalena; Moser, Dirk A; Simon, Perikles

2012-11-01

Gene doping--or the abuse of gene therapy--will continue to threaten the sports world. History has shown that progress in medical research is likely to be abused in order to enhance human performance. In this review, we critically discuss the progress and the risks associated with the field of erythropoietin (EPO) gene therapy and its applicability to EPO gene doping. We present typical vector systems that are employed in ex vivo and in vivo gene therapy trials. Due to associated risks, gene doping is not a feasible alternative to conventional EPO or blood doping at this time. Nevertheless, it is well described that about half of the elite athlete population is in principle willing to risk its health to gain a competitive advantage. This includes the use of technologies that lack safety approval. Sophisticated detection approaches are a prerequisite for prevention of unapproved and uncontrolled use of gene therapy technology. In this review, we present current detection approaches for EPO gene doping, with a focus on blood-based direct and indirect approaches. Gene doping is detectable in principle, and recent DNA-based detection strategies enable long-term detection of transgenic DNA (tDNA) following in vivo gene transfer. Copyright © 2012 John Wiley & Sons, Ltd.

A Quarter Century of Doping Scandals

DEFF Research Database (Denmark)

Gleaves, John; Christiansen, Ask Vest

2013-01-01

because it marked the first time a high-profile athlete was unceremoniously stripped of his medal rather than having his results covered up or ignored. Johnson’s case is also useful for framing the ongoing issue with doping in elite sports while providing some insight into the current problem sport faces.......With the ongoing doping scandals, revelations, and confessions, it was likely that few celebrated this autumn’s significant anniversary in doping history. Twenty-five years ago—September 26, 1988—news broke of the first major doping scandal in the Olympic Games. Canadian sprinter Ben Johnson, who...... just two days previously had won the 100 meter dash in a world record clip, had tested positive for the banned anabolic steroid stanozolol at the Seoul Olympics. Johnson was neither the first to use prohibited “doping” substances at the Olympics nor the first to get caught. Johnson’s case is notable...

Preparation of Polyaniline-Doped Fullerene Whiskers

Directory of Open Access Journals (Sweden)

Bingzhe Wang

2013-01-01

Full Text Available Fullerene C60 whiskers (FWs doped with polyaniline emeraldine base (PANI-EB were synthesized by mixing PANI-EB/N-methyl pyrrolidone (NMP colloid and FWs suspension based on the nature of the electron acceptor of C60 and electron donor of PANI-EB. Scanning electron microscopy (SEM, Fourier transform infrared (FT-IR, and ultraviolet-visible (UV-Vis spectra characterized the morphology and molecular structure of the FWs doped with PANI-EB. SEM observation showed that the smooth surface of FWs was changed to worm-like surface morphology after being doped with PANI-EB. The UV-Vis spectra suggested that charge-transfer (CT complex of C60 and PANI-EB was formed as PANI-EBδ+-C60δ-. PANI-EB-doped FWs might be useful as a new type of antibacterial and self-cleaning agent as well as multifunctional material to improve the human health and living environment.

Insight into doping efficiency of organic semiconductors from the analysis of the density of states in n-doped C60 and ZnPc

Science.gov (United States)

Gaul, Christopher; Hutsch, Sebastian; Schwarze, Martin; Schellhammer, Karl Sebastian; Bussolotti, Fabio; Kera, Satoshi; Cuniberti, Gianaurelio; Leo, Karl; Ortmann, Frank

2018-05-01

Doping plays a crucial role in semiconductor physics, with n-doping being controlled by the ionization energy of the impurity relative to the conduction band edge. In organic semiconductors, efficient doping is dominated by various effects that are currently not well understood. Here, we simulate and experimentally measure, with direct and inverse photoemission spectroscopy, the density of states and the Fermi level position of the prototypical materials C60 and zinc phthalocyanine n-doped with highly efficient benzimidazoline radicals (2-Cyc-DMBI). We study the role of doping-induced gap states, and, in particular, of the difference Δ1 between the electron affinity of the undoped material and the ionization potential of its doped counterpart. We show that this parameter is critical for the generation of free carriers and influences the conductivity of the doped films. Tuning of Δ1 may provide alternative strategies to optimize the electronic properties of organic semiconductors.

Nonlinear Elasticity of Doped Semiconductors

Science.gov (United States)

2017-02-01

AFRL-RY-WP-TR-2016-0206 NONLINEAR ELASTICITY OF DOPED SEMICONDUCTORS Mark Dykman and Kirill Moskovtsev Michigan State University...2016 4. TITLE AND SUBTITLE NONLINEAR ELASTICITY OF DOPED SEMICONDUCTORS 5a. CONTRACT NUMBER FA8650-16-1-7600 5b. GRANT NUMBER 5c. PROGRAM...vibration amplitude. 15. SUBJECT TERMS semiconductors , microresonators, microelectromechanical 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

Nitrogen-doped carbon aerogels for electrical energy storage

Science.gov (United States)

Campbell, Patrick; Montalvo, Elizabeth; Baumann, Theodore F.; Biener, Juergen; Merrill, Matthew; Reed, Eric W.; Worsley, Marcus A.

2017-10-03

Disclosed here is a method for making a nitrogen-doped carbon aerogel, comprising: preparing a reaction mixture comprising formaldehyde, at least one nitrogen-containing resorcinol analog, at least one catalyst, and at least one solvent; curing the reaction mixture to produce a wet gel; drying the wet gel to produce a dry gel; and thermally annealing the dry gel to produce the nitrogen-doped carbon aerogel. Also disclosed is a nitrogen-doped carbon aerogel obtained according to the method and a supercapacitor comprising the nitrogen-doped carbon aerogel.

Tunneling spectroscopy of heavily underdoped crystals of Bi2Sr2CaCu2O8+δ

International Nuclear Information System (INIS)

Ozyuzer, L.; Zasadzinski, J.F.; Miyakawa, N.; Kendziora, C.; Jian, S.; Hinks, D. G.; Gray, K.E.

2000-01-01

Crystals of Bi 2 Sr 2 CaCu 2 O 8+δ with optimal Tc = 95 K have been underdoped using two different methods and the superconducting gaps have been obtained by tunneling. In some cases, three different tunneling geometries have been utilized: point contact, STM and break junctions. The first doping method involves control of the oxygen content by annealing in various partial pressures of oxygen. These crystals exhibit a narrow spread of gap values over a wide doping range from overdoped (Tc = 56 K) to underdoped with Tc = 70 K. However, for underdoped crystals with Tc midpoints in the range 25 K--63 K, there is a dramatic increase in the spread of gap values which may signal the development of static phase separation of either chemical or electronic origin. To avoid possible chemical phase separation, the authors have explored another doping procedure which incorporates Dy substitution on the Ca site. These crystals exhibit a relatively narrow superconducting transition width and some preliminary tunneling spectra will be presented

White light emission from engineered silicon carbide

DEFF Research Database (Denmark)

Ou, Haiyan

Silicon carbide (SiC) is a wide indirect bandgap semiconductor. The light emission efficiency is low in nature. But this material has very unique physical properties like good thermal conductivity, high break down field etc in addition to its abundance. Therefore it is interesting to engineer its...... light emission property so that to take fully potential applications of this material. In this talk, two methods, i.e. doping SiC heavily by donor-acceptor pairs and making SiC porous are introduced to make light emission from SiC. By co-doping SiC with nitrogen and boron heavily, strong yellow emission...... is demonstrated. After optimizing the passivation conditions, strong blue-green emission from porous SiC is demonstrated as well. When combining the yellow emission from co-doped SiC and blue-green from porous SiC, a high color rendering index white light source is achieved....

On magnetic ordering in heavily sodium substituted hole doped lanthanum manganites

Energy Technology Data Exchange (ETDEWEB)

Sethulakshmi, N. [Department of Physics, Cochin University of Science and Technology, Cochin 682022, Kerala (India); Unnimaya, A.N. [Centre for Materials for Electronic Technology (CMET), Thrissur 680581, Kerala (India); Al-Omari, I.A.; Al-Harthi, Salim [Department of Physics, Sultan Qaboos University, PC 123 Muscat (Oman); Sagar, S. [Government College for Women, Thiruvananthapuram 695014, Kerala (India); Thomas, Senoy [Materials Science and Technology Division, National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram 695019, Kerala (India); Srinivasan, G. [Department of Physics, Oakland University, Rochester (United States); Anantharaman, M.R., E-mail: mraiyer@yahoo.com [Department of Physics, Cochin University of Science and Technology, Cochin 682022, Kerala (India)

2015-10-01

Mixed valence manganite system with monovalent sodium substituted lanthanum manganites form the basis of the present work. Lanthanum manganites belonging to the series La{sub 1−x}Na{sub x}MnO{sub 3} with x=0.5–0.9 were synthesized using modified citrate gel method. Variation of lattice parameters and unit cell volume with Na concentration were analyzed and the magnetization measurements indicated ferromagnetic ordering in all samples at room temperature. Low temperature magnetization behavior indicated that all samples exhibit antiferromagnetism along with ferromagnetism and it has also been observed that antiferromagnetic ordering dominates ferromagnetic ordering as concentration is increased. Evidence for such a magnetic inhomogeneity in these samples has been confirmed from the variation in Mn{sup 3+}/Mn{sup 4+} ion ratio from X-ray Photoelectron Spectroscopy and from the absorption peak studies using Ferromagnetic Resonance Spectroscopy. - Highlights: • Higher substitution of more than 50 percent of monovalent ion, sodium for La sites in lanthanum manganites scarce in literature. • Structural studies using XRD and further structure refinement by Rietveld refinement confirmed orthorhombic pbnm spacegroup. • Ferromagnetic behavior at room temperature with saturation magnetization decreasing with increase in sodium concentration. • M vs T measurements using FC ZFC proved coexisting FM/AFM behavior arising from exchange interactions between different valence states of Mn ions. • Disparity in ratio of Mn valence ions indicated presence of vacancies providing the role of vacancies and oxygen stoichiometry in deciding magnetic inhomogeneity.

Phase transitions and doping in semiconductor nanocrystals

Science.gov (United States)

Sahu, Ayaskanta

Colloidal semiconductor nanocrystals are a promising technological material because their size-dependent optical and electronic properties can be exploited for a diverse range of applications such as light-emitting diodes, bio-labels, transistors, and solar cells. For many of these applications, electrical current needs to be transported through the devices. However, while their solution processability makes these colloidal nanocrystals attractive candidates for device applications, the bulky surfactants that render these nanocrystals dispersible in common solvents block electrical current. Thus, in order to realize the full potential of colloidal semiconductor nanocrystals in the next-generation of solid-state devices, methods must be devised to make conductive films from these nanocrystals. One way to achieve this would be to add minute amounts of foreign impurity atoms (dopants) to increase their conductivity. Electronic doping in nanocrystals is still very much in its infancy with limited understanding of the underlying mechanisms that govern the doping process. This thesis introduces an innovative synthesis of doped nanocrystals and aims at expanding the fundamental understanding of charge transport in these doped nanocrystal films. The list of semiconductor nanocrystals that can be doped is large, and if one combines that with available dopants, an even larger set of materials with interesting properties and applications can be generated. In addition to doping, another promising route to increase conductivity in nanocrystal films is to use nanocrystals with high ionic conductivities. This thesis also examines this possibility by studying new phases of mixed ionic and electronic conductors at the nanoscale. Such a versatile approach may open new pathways for interesting fundamental research, and also lay the foundation for the creation of novel materials with important applications. In addition to their size-dependence, the intentional incorporation of

The importance of cooling of urine samples for doping analysis

NARCIS (Netherlands)

Kuenen, J. Gijs; Konings, Wil N.

Storing and transporting of urine samples for doping analysis, as performed by the anti-doping organizations associated with the World Anti-Doping Agency, does not include a specific protocol for cooled transport from the place of urine sampling to the doping laboratory, although low cost cooling

p-type doping by platinum diffusion in low phosphorus doped silicon

Science.gov (United States)

Ventura, L.; Pichaud, B.; Vervisch, W.; Lanois, F.

2003-07-01

In this work we show that the cooling rate following a platinum diffusion strongly influences the electrical conductivity in weakly phosphorus doped silicon. Diffusions were performed at the temperature of 910 °C in the range of 8 32 hours in 0.6, 30, and 60 Ωrm cm phosphorus doped silicon samples. Spreading resistance profile analyses clearly show an n-type to p-type conversion under the surface when samples are cooled slowly. On the other hand, a compensation of the phosphorus donors can only be observed when samples are quenched. One Pt related acceptor deep level at 0.43 eV from the valence band is assumed to be at the origin of the type conversion mechanism. Its concentration increases by lowering the applied cooling rate. A complex formation with fast species such as interstitial Pt atoms or intrinsic point defects is expected. In 0.6 Ωrm cm phosphorus doped silicon, no acceptor deep level in the lower band gap is detected by DLTS measurement. This removes the opportunity of a pairing between phosphorus and platinum and suggests the possibility of a Fermi level controlled complex formation.

Blood doping at the Olympic Games.

Science.gov (United States)

Fitch, Kenneth D

2017-11-01

The objective of this paper was to review our knowledge of athletes who have, are believed to have or have attempted to engage in blood doping to enhance their performance at an Olympic Games. The paper focused on the Games from Munich 1972 to London 2012 and the author had a medical role at each of the Olympics that is discussed. The study revealed that Olympic athletes have benefitted from manipulating their blood by re-infusion of autologous or infusion of homologous blood and by administering erythropoiesis stimulating agents, notably the three generations of erythropoietins. Fifty seven athletes have been sanctioned with 12 athletes forfeiting 17 Olympic medals including 12 gold medals because of blood doping. Until 1986, the infusion of blood was not prohibited in sport but considered unethical. Erythropoietin was prohibited by the International Olympic Committee's Medical Commission in 1990. There has been a change as to how Olympic athletes have enhanced performance by blood doping, commencing with blood infusion and later administering erythropoiesis stimulating agents and significant advances have occurred in detecting such misuse. Currently, the hematological component of World Anti-Doping Agency's athlete biological passport is an important but not infallible mechanism to identify athletes who cheat by blood doping.

Electrospark doping of steel with tungsten

International Nuclear Information System (INIS)

Denisova, Yulia; Shugurov, Vladimir; Petrikova, Elizaveta; Seksenalina, Malika; Ivanova, Olga; Ikonnikova, Irina; Kunitsyna, Tatyana; Vlasov, Victor; Klopotov, Anatoliy; Ivanov, Yuriy

2016-01-01

The paper is devoted to the numerical modeling of thermal processes and the analysis of the structure and properties of the surface layer of carbon steel subjected to electrospark doping with tungsten. The problem of finding the temperature field in the system film (tungsten) / substrate (iron) is reduced to the solution of the heat conductivity equation. A one-dimensional case of heating and cooling of a plate with the thickness d has been considered. Calculations of temperature fields formed in the system film / substrate synthesized using methods of electrospark doping have been carried out as a part of one-dimensional approximation. Calculations have been performed to select the mode of the subsequent treatment of the system film / substrate with a high-intensity pulsed electron beam. Authors revealed the conditions of irradiation allowing implementing processes of steel doping with tungsten. A thermodynamic analysis of phase transformations taking place during doping of iron with tungsten in equilibrium conditions has been performed. The studies have been carried out on the surface layer of the substrate modified using the method of electrospark doping. The results showed the formation in the surface layer of a structure with a highly developed relief and increased strength properties

Electrospark doping of steel with tungsten

Energy Technology Data Exchange (ETDEWEB)

Denisova, Yulia, E-mail: yukolubaeva@mail.ru; Shugurov, Vladimir, E-mail: shugurov@opee.hcei.tsc.ru [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 634055, Russia, Tomsk, 2/3 Akademicheskiy Ave (Russian Federation); Petrikova, Elizaveta, E-mail: elizmarkova@yahoo.com [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 634055, Russia, Tomsk, 2/3 Akademicheskiy Ave (Russian Federation); National Research Tomsk State University, 36 Lenin Str. Tomsk, 634050 (Russian Federation); Seksenalina, Malika, E-mail: sportmiss@bk.ru [National Research Tomsk Polytechnic University, 30 Lenin Str. Tomsk, 634050 (Russian Federation); Ivanova, Olga, E-mail: ivaov@mail.ru; Ikonnikova, Irina, E-mail: irinaikonnikova@yandex.ru [Tomsk State University of Architecture and Building, 2 Solyanaya Sq. Tomsk, 634003 (Russian Federation); Kunitsyna, Tatyana, E-mail: kma11061990@mail.ru; Vlasov, Victor, E-mail: rector@tsuab.ru [National Research Tomsk Polytechnic University, 30 Lenin Str. Tomsk, 634050 (Russian Federation); Tomsk State University of Architecture and Building, 2 Solyanaya Sq. Tomsk, 634003 (Russian Federation); Klopotov, Anatoliy, E-mail: klopotovaa@tsuab.ru [National Research Tomsk State University, 36 Lenin Str. Tomsk, 634050 (Russian Federation); Tomsk State University of Architecture and Building, 2 Solyanaya Sq. Tomsk, 634003 (Russian Federation); Ivanov, Yuriy, E-mail: yufi55@mail.ru [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 634055, Russia, Tomsk, 2/3 Akademicheskiy Ave (Russian Federation); National Research Tomsk State University, 36 Lenin Str. Tomsk, 634050 (Russian Federation); National Research Tomsk Polytechnic University, 30 Lenin Str. Tomsk, 634050 (Russian Federation)

2016-01-15

The paper is devoted to the numerical modeling of thermal processes and the analysis of the structure and properties of the surface layer of carbon steel subjected to electrospark doping with tungsten. The problem of finding the temperature field in the system film (tungsten) / substrate (iron) is reduced to the solution of the heat conductivity equation. A one-dimensional case of heating and cooling of a plate with the thickness d has been considered. Calculations of temperature fields formed in the system film / substrate synthesized using methods of electrospark doping have been carried out as a part of one-dimensional approximation. Calculations have been performed to select the mode of the subsequent treatment of the system film / substrate with a high-intensity pulsed electron beam. Authors revealed the conditions of irradiation allowing implementing processes of steel doping with tungsten. A thermodynamic analysis of phase transformations taking place during doping of iron with tungsten in equilibrium conditions has been performed. The studies have been carried out on the surface layer of the substrate modified using the method of electrospark doping. The results showed the formation in the surface layer of a structure with a highly developed relief and increased strength properties.

Doping prevention: Experience of Antidoping Agency of Serbia

Directory of Open Access Journals (Sweden)

Dikić Nenad

2016-01-01

Full Text Available By signing the Copenhagen Declaration on Doping in Sport, in December 2003, the basis was created for the adoption of the Law on prevention of doping in sports. The Parliament of Serbia has adopted this law firstly in 2005, on the basis of which was established Antidoping Agency of Serbia (ADAS. Due to changes, which are done on the World Antidoping Code, the Parliament of Serbia has adopted a new Law on the Prevention of doping in sport in 2014. Behind all these legislative and governmental activity, however, there is a long experience and knowledge of members of the Sports Medicine Association of Serbia, who conducted the doping control when there was no official agency and started a new activity that, until then, doctors did not practice. Not only that, ADAS is one of the few antidoping organization in the world where only the people in health profession are working as a doping control officers. ADAS set the highest standards that have the most important international federations (FIBA, UEFA, FIFA etc. and not more than 20% of national antidoping organization. For this we are very proud, because we have created an institution that represents the heritage for the future generations of medical doctors. By the time ADAS has been established, it was considered there is no problem of doping in Serbia. However, the number of doping positive cases clearly supports the fact that the problem exists. Over the years, the number of athletes who are tested positive, have decreased, primarily due to hard work on education, not only of the athletes, but also of the other sports officials. From the period of establishment until January 1, 2016, ADAS has completed a total of 5974 doping controls and 62 athletes have been tested positive for doping on over 70 different banned substances.

Doping control analyses in horseracing: a clinician's guide.

Science.gov (United States)

Wong, Jenny K Y; Wan, Terence S M

2014-04-01

Doping(1) in sports is highly detrimental, not only to the athletes involved but to the sport itself as well as to the confidence of the spectators and other participants. To protect the integrity of any sport, there must be in place an effective doping control program. In human sports, a 'top-down' and generally unified approach is taken where the rules and regulations against doping for the majority of elite sport events held in any country are governed by the World Anti-Doping Agency (WADA). However, in horseracing, there is no single organisation regulating this form of equestrian sport; instead, the rules and regulations are provided by individual racing authorities and so huge variations exist in the doping control programs currently in force around the world. This review summarises the current status of doping control analyses in horseracing, from sample collection, to the analyses of the samples, and to the need for harmonisation as well as exploring some of the difficulties currently faced by racing authorities, racing chemists and regulatory veterinarians worldwide. Copyright © 2014 Elsevier Ltd. All rights reserved.

Remote Molecular Doping of Colloidal Quantum Dot Photovoltaics

KAUST Repository

Kirmani, Ahmad R.

2016-10-07

In recent years colloidal quantum dot (CQD) photovoltaics have developed rapidly because of novel device architectures and robust surface passivation schemes. Achieving controlled net doping remains an important unsolved challenge for this field. Herein we present a general molecular doping platform for CQD solids employing a library of metal–organic complexes. Low effective ionization energy and high electron affinity complexes are shown to produce n- and p-doped CQD solids. We demonstrate the obvious advantage in solar cells by p-doping the CQD absorber layer. Employing photoemission spectroscopy, we identify two doping concentration regimes: lower concentrations lead to efficient doping, while higher concentrations also cause large surface dipoles creating energy barriers to carrier flow. Utilizing the lower concentration regime, we remove midgap electrons leading to 25% enhancement in the power conversion efficiency relative to undoped cells. Given the vast number of available metal–organic complexes, this approach opens new and facile routes to tuning the properties of CQDs for various applications without necessarily resorting to new ligand chemistries.

Study of Si-Ge interdiffusion with phosphorus doping

KAUST Repository

Cai, Feiyang; Anjum, Dalaver H.; Zhang, Xixiang; Xia, Guangrui

2016-01-01

Si-Ge interdiffusion with phosphorus doping was investigated by both experiments and modeling. Ge/Si1-x Ge x/Ge multi-layer structures with 0.75doping, and a dislocation density of 108 to 109 cm−2 range were studied. The P-doped sample shows an accelerated Si-Ge interdiffusivity, which is 2–8 times of that of the undoped sample. The doping dependence of the Si-Ge interdiffusion was modelled by a Fermi-enhancement factor. The results show that the Si-Ge interdiffusion coefficient is proportional to n2/n2i for the conditions studied, which indicates that the interdiffusion in a high Ge fraction range with n-type doping is dominated by V2− defects. The Fermi-enhancement factor was shown to have a relatively weak dependence on the temperature and the Ge fraction. The results are relevant to the structure and thermal processing condition design of n-type doped Ge/Si and Ge/SiGe based devices such as Ge/Si lasers.

Remote Molecular Doping of Colloidal Quantum Dot Photovoltaics

KAUST Repository

Kirmani, Ahmad R.; Kiani, Amirreza; Said, Marcel M.; Voznyy, Oleksandr; Wehbe, Nimer; Walters, Grant; Barlow, Stephen; Sargent, Edward H.; Marder, Seth R.; Amassian, Aram

2016-01-01

In recent years colloidal quantum dot (CQD) photovoltaics have developed rapidly because of novel device architectures and robust surface passivation schemes. Achieving controlled net doping remains an important unsolved challenge for this field. Herein we present a general molecular doping platform for CQD solids employing a library of metal–organic complexes. Low effective ionization energy and high electron affinity complexes are shown to produce n- and p-doped CQD solids. We demonstrate the obvious advantage in solar cells by p-doping the CQD absorber layer. Employing photoemission spectroscopy, we identify two doping concentration regimes: lower concentrations lead to efficient doping, while higher concentrations also cause large surface dipoles creating energy barriers to carrier flow. Utilizing the lower concentration regime, we remove midgap electrons leading to 25% enhancement in the power conversion efficiency relative to undoped cells. Given the vast number of available metal–organic complexes, this approach opens new and facile routes to tuning the properties of CQDs for various applications without necessarily resorting to new ligand chemistries.

Study of Si-Ge interdiffusion with phosphorus doping

KAUST Repository

Cai, Feiyang

2016-10-28

Si-Ge interdiffusion with phosphorus doping was investigated by both experiments and modeling. Ge/Si1-x Ge x/Ge multi-layer structures with 0.75doping, and a dislocation density of 108 to 109 cm−2 range were studied. The P-doped sample shows an accelerated Si-Ge interdiffusivity, which is 2–8 times of that of the undoped sample. The doping dependence of the Si-Ge interdiffusion was modelled by a Fermi-enhancement factor. The results show that the Si-Ge interdiffusion coefficient is proportional to n2/n2i for the conditions studied, which indicates that the interdiffusion in a high Ge fraction range with n-type doping is dominated by V2− defects. The Fermi-enhancement factor was shown to have a relatively weak dependence on the temperature and the Ge fraction. The results are relevant to the structure and thermal processing condition design of n-type doped Ge/Si and Ge/SiGe based devices such as Ge/Si lasers.

Psychological and social correlates of doping attitudes among Italian athletes.

Science.gov (United States)

Zucchetti, Giulia; Candela, Filippo; Villosio, Carlo

2015-02-01

This study aims to identify the main psychological and social correlates of doping attitudes among Italian athletes. It is well recognized that athlete disposition and attitude towards doping is one of the factors responsible for doping behavior. Less is known, however, about the factors that sustain the level of athletes' attitudes towards doping. The main psychological (i.e., perfectionism, sport motivation, self-confidence and life satisfaction) and social correlates (i.e., social network and contact with people who use sports drugs) of attitudes towards doping among Italian athletes are examined in this paper. Differences are hypothesized regarding the type of sport (resistance sport vs. non-resistance sport) and athlete participation in competitive sport (i.e., agonistics) or in non-competitive sport (i.e., amateurs) on the level of attitude towards doping. The research hypothesis is that each of these constructs affects the level of athletes' attitudes toward doping. Data were collected from a sample of athletes (N=109), aged from 15 to 45 (M=31.5; SD=13.78) recruited in a Sports Medicine Center. Socio-demographic information, attitude towards doping, psychological and social variables were assessed through self-report questionnaire. Hierarchical multiple regression showed that both psychological (i.e., extrinsic motivation, perfectionism) and social variables (i.e., athletes' contact with doping users) were associated with athletes' attitudes towards doping. The results highlighted that athletes with excessive perfectionism, extrinsically motivated and who have contact with doping users have a positive attitude toward doping. Athletes who exhibit these characteristics should be considered at risk and monitored to prevent possible future sports drug use. Copyright © 2014 Elsevier B.V. All rights reserved.

Statistical transmutation in doped quantum dimer models.

Science.gov (United States)

Lamas, C A; Ralko, A; Cabra, D C; Poilblanc, D; Pujol, P

2012-07-06

We prove a "statistical transmutation" symmetry of doped quantum dimer models on the square, triangular, and kagome lattices: the energy spectrum is invariant under a simultaneous change of statistics (i.e., bosonic into fermionic or vice versa) of the holes and of the signs of all the dimer resonance loops. This exact transformation enables us to define the duality equivalence between doped quantum dimer Hamiltonians and provides the analytic framework to analyze dynamical statistical transmutations. We investigate numerically the doping of the triangular quantum dimer model with special focus on the topological Z(2) dimer liquid. Doping leads to four (instead of two for the square lattice) inequivalent families of Hamiltonians. Competition between phase separation, superfluidity, supersolidity, and fermionic phases is investigated in the four families.

Substitutional Doping for Aluminosilicate Mineral and Superior Water Splitting Performance

Science.gov (United States)

Zhang, Yi; Fu, Liangjie; Shu, Zhan; Yang, Huaming; Tang, Aidong; Jiang, Tao

2017-07-01

Substitutional doping is a strategy in which atomic impurities are optionally added to a host material to promote its properties, while the geometric and electronic structure evolution of natural nanoclay mineral upon substitutional metal doping is still ambiguous. This paper first designed an efficient lanthanum (La) doping strategy for nanotubular clay (halloysite nanotube, HNT) through the dynamic equilibrium of a substitutional atom in the presence of saturated AlCl3 solution, and systematic characterization of the samples was performed. Further density functional theory (DFT) calculations were carried out to reveal the geometric and electronic structure evolution upon metal doping, as well as to verify the atom-level effect of the La doping. The CdS loading and its corresponding water splitting performance could demonstrate the effect of La doping. CdS nanoparticles (11 wt.%) were uniformly deposited on the surface of La-doped halloysite nanotube (La-HNT) with the average size of 5 nm, and the notable photocatalytic hydrogen evolution rate of CdS/La-HNT reached up to 47.5 μmol/h. The results could provide a new strategy for metal ion doping and constructive insight into the substitutional doping mechanism.

How lithium atoms affect the first hyperpolarizability of BN edge-doped graphene.

Science.gov (United States)

Song, Yao-Dong; Wu, Li-Ming; Chen, Qiao-Ling; Liu, Fa-Kun; Tang, Xiao-Wen

2016-01-01

How do lithium atoms affect the first hyperpolarizability (β0) of boron-nitrogen (BN) edge-doped graphene. In this work, using pentacene as graphene model, Lin@BN-1 edge-doped pentacene and Lin@BN-2 edge-doped pentacene (n = 1, 5) were designed to study this problem. First, two models (BN-1 edge-doped pentacene, and BN-2 edge-doped pentacene ) were formed by doping the BN into the pentacene with different order, and then Li@BN-1 edge-doped pentacene and Li@ BN-2 edge-doped pentacene were obtained by substituting the H atom in BN edge-doped pentacene with a Li atom. The results show that the first hyperpolarizabilities of BN-1 edge-doped pentacene and Li@BN-1 edge-doped pentacene were 4059 a.u. and 6249 a.u., respectively; the first hyperpolarizabilities of BN-2 edge-doped pentacene and Li@BN-2 edge-doped pentacene were 2491 a.u. and 4265 a.u., respectively. The results indicate that the effect of Li substitution is to greatly increase the β0 value. To further enhance the first hyperpolarizability, Li5@ BN-1 edge-doped pentacene and Li5@BN-2 edge-doped pentacene were designed, and were found to exhibit considerably larger first hyperpolarizabilities (β0) (12,112 a.u. and 7921a.u., respectively). This work may inspire further study of the nonlinear properties of BN edge-doped graphene.

Performance enhancement of polymer Schottky diode by doping pentacene

International Nuclear Information System (INIS)

Kang, K.S.; Chen, Y.; Lim, H.K.; Cho, K.Y.; Han, K.J.; Kim, Jaehwan

2009-01-01

Schottky diodes have been fabricated using pentacene-doped poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) as a semiconducting material. To understand the fundamental properties of the pentacene-doped PEDOT:PSS, ultraviolet visible (UV) absorption spectroscopy was employed. It was found that a significant amount of pentacene can dissolve in n-methylpyrrolidone solvent. No characteristic absorption peak of pentacene was observed in the UV-visible spectra of PEDOT:PSS films doped with pentacene,. However, the absorption intensity of the doped PEDOT:PSS films increased as the pentacene concentration increased in particular in the UV region. The atomic force microscope images show that the surface roughnesses of PEDOT:PSS films increased as the pentacene concentration increased. Three-layer Schottky diodes comprising Al/PEDOT:PSS/Au or Al/PEDOT:PSS-pentacene/Au were fabricated. The maximum forward currents of non-doped and doped Schottky diodes were 4.8 and 440 μA/cm 2 at 3.3 MV/m, respectively. The forward current increased nearly two orders of magnitude for Schottky diode doped with 11.0 wt.% of pentacene.

Perovskite-Perovskite Homojunctions via Compositional Doping.

Science.gov (United States)

Dänekamp, Benedikt; Müller, Christian; Sendner, Michael; Boix, Pablo P; Sessolo, Michele; Lovrincic, Robert; Bolink, Henk J

2018-05-11

One of the most important properties of semiconductors is the possibility of controlling their electronic behavior via intentional doping. Despite the unprecedented progress in the understanding of hybrid metal halide perovskites, extrinsic doping of perovskite remains nearly unexplored and perovskite-perovskite homojunctions have not been reported. Here we present a perovskite-perovskite homojunction obtained by vacuum deposition of stoichiometrically tuned methylammonium lead iodide (MAPI) films. Doping is realized by adjusting the relative deposition rates of MAI and PbI 2 , obtaining p-type (MAI excess) and n-type (MAI defect) MAPI. The successful stoichiometry change in the thin films is confirmed by infrared spectroscopy, which allows us to determine the MA content in the films. We analyzed the resulting thin-film junction by cross-sectional scanning Kelvin probe microscopy (SKPM) and found a contact potential difference (CPD) of 250 mV between the two differently doped perovskite layers. Planar diodes built with the perovskite-perovskite homojunction show the feasibility of our approach for implementation in devices.

Structure prediction of boron-doped graphene by machine learning

Science.gov (United States)

M. Dieb, Thaer; Hou, Zhufeng; Tsuda, Koji

2018-06-01

Heteroatom doping has endowed graphene with manifold aspects of material properties and boosted its applications. The atomic structure determination of doped graphene is vital to understand its material properties. Motivated by the recently synthesized boron-doped graphene with relatively high concentration, here we employ machine learning methods to search the most stable structures of doped boron atoms in graphene, in conjunction with the atomistic simulations. From the determined stable structures, we find that in the free-standing pristine graphene, the doped boron atoms energetically prefer to substitute for the carbon atoms at different sublattice sites and that the para configuration of boron-boron pair is dominant in the cases of high boron concentrations. The boron doping can increase the work function of graphene by 0.7 eV for a boron content higher than 3.1%.

FLUX PINNING EFFECTS IN Ag-DOPED YBCO (123 SUPERCONDUCTOR

Directory of Open Access Journals (Sweden)

Madelen Pérez

2010-07-01

Full Text Available Polycrystalline samples of Ag+-doped YBCO (123 (YBa2 (Cu1-xAgx3O7-δwith 0≤x≤0.3 were produced by solid state reaction method. The Ag- doped YBCO samples showed higher critical current densities (Jc with a Jc maximum for samples doped with x=0.05. This behavior can be assigned to an increase of pinning forces. The irreversibility temperature (Tirr, also increased in doped samples as a function of Ag content, with the highest temperature for the sample doped with x=0.05, wich correlates well with the observed Jc increasing. However, samples doped with x>0.05 displayed a decreasing of electrical properties (less Tirr, less Jc, etc. atributed to an excess of Ag in the grain boundaries which, reduces the grain sizes and increases the number of weak- links.

Copper doped borate dosimeters revisited